GENERAL ACCOUNT OF THE SKELETON IN MAMMALIA (CONTINUED).
THE SKULL AND APPENDICULAR SKELETON.
THE SKULL.
MONOTREMATA. In both genera the cranium is thin-walled, has a fairly
large cavity, and is very smooth and rounded externally. The sutures
between many of the bones early become obliterated in a manner
comparable to that in birds, and the facial portion of the skull is
much prolonged.
In _Echidna_ the face is drawn out into a gradually tapering rostrum,
formed mainly by the premaxillae, maxillae and nasals. The zygomatic
arch is very weak, and the palate extends very far back. The tympanic
forms a slender ring. The mandible is extremely slight, with no
ascending portion, and but slight traces of the coronoid process and
angle. The hyoid has a wide basi-hyal and stout thyro-hyals, while the
anterior cornua are slender, and include ossified epi-hyals and
cerato-hyals.
In _Ornithorhynchus_ the zygomatic arch is much stouter than in
_Echidna_. The face is produced into a wide beak, mainly supported by
the premaxillae, between whose diverging anterior ends there is a
dumb-bell-shaped bone. The maxillae are flattened below, and each
bears a large horny tooth, which meets a corresponding structure borne
on a surface near the middle of the mandible. The mandible is
considerably stouter than in _Echidna_, but the angle and coronoid
process are but little developed. The infra-orbital foramen and the
inferior dental and mental foramina of the mandible are all very
large.
[Illustration FIG. 90. HALF FRONT VIEW[165] OF THE SKULLS OF A
TASMANIAN WOLF (_Thylacinus cynocephalus_) (to the left) × 3/8; AND OF
A HAIRY-NOSED WOMBAT (_Phascolomys latifrons_) (to the right) × 3/8.
(Camb. Mus.)
1. premaxillae.
2. nasal.
3. frontal.
4. infra-orbital foramen.
5. lachrymal.
6. jugal.
7. coronoid process of the mandible.
8. lachrymal foramen.
i. 1. first upper incisor.
C. canine.]
MARSUPIALIA. The skulls of the various types of the Marsupials
frequently bear a strong superficial resemblance to those of some of
the different groups of placental mammals. Thus the skull of the
Dasyuridae resembles that of the Carnivora, the resemblance being most
marked between the skulls of _Thylacinus_ and the dog. The skull of
_Notoryctes_ is strongly suggestive of that of an Insectivore, and
that of other Marsupials such as the wombat, recalls equally the
characteristic features of a Rodent's skull. But, however much they
may differ from one another, the skulls of all Marsupials agree in the
following respects. (1) The brain cavity, and especially the cerebral
fossa, has a very small comparative size. (2) The nasals are always
large, and the mesethmoid is extensively ossified, and terminated by a
prominent vertical edge. (3) Processes from the jugal and frontal in
living forms never meet and enclose the orbit, but the zygomatic arch
is always complete. (4) The jugal always extends back to form part of
the glenoid fossa. (5) The lachrymal canal opens either external to or
upon the margin of the orbit, and the nasal processes of the
premaxillae never quite reach the frontals. (6) The posterior part of
the palate is commonly pierced by large oval vacuities. (7) The
tympanic is small and never fused to the bones of the cranium. (8) The
carotid canal perforates the basisphenoid and not the tympanic bulla.
(9) The optic foramen and sphenoidal fissure are confluent. (10) In
every case except _Tarsipes_ the angle of the mandible is more or less
inflected.
The skull of the extinct _Thylacoleo_ differs from that of all other
Marsupials in the fact that the postorbital bar is complete. The hyoid
is constructed on much the same plan in all Marsupials. It consists of
a small basi-hyal, a pair of broad cerato-hyals, and a pair of strong
thyro-hyals. The epi-hyals and stylo-hyals are generally unossified.
EDENTATA. In Sloths (Bradypodidae) the sutures become early
obliterated, the cranial portion of the skull is rather high, and the
facial portion very short. The lachrymal is very small, and its canal
opens outside the orbit. The zygomatic arch is incomplete, and the
jugal (fig. 91, 5) is curiously forked, but in a manner differing in
the two genera. The premaxillae are very small,--in _Bradypus_ quite
vestigial. The mandible is well developed, the angle being specially
marked in _Bradypus_. In _Choloepus_ the symphysial part is drawn out
in a somewhat spout-like manner (fig. 91, 6). In both genera the
thyro-hyals are ankylosed with the basi-hyal.
[Illustration FIG. 91. SKULL OF A TWO-FINGERED SLOTH (_Choloepus
didactylus_) × 1/2. (Camb. Mus.)
1. anterior nares.
2. postorbital process of the frontal.
3. coronoid process.
4. angle of the mandible.
5. jugal.
6. spout-like prolongation of the mandible.]
In _Megatherium_ the general appearance of the skull is distinctly
sloth-like, but the facial portion is more elongated, partly owing to
the development of a prenasal bone, and the zygomatic arch is
complete. The mandible is very deep in the middle, and is drawn out
into a long spout-like process in front.
Anteaters (Myrmecophagidae) have a much modified skull, and this is
especially the case in the Great Anteater, _Myrmecophaga_. The skull
is smooth and evenly-rounded, in these respects recalling that of
_Echidna_, but it is longer and tapers much more gradually than in
_Echidna_. The occipital condyles are remarkably large. The premaxillae
are small, and the long rostrum is chiefly composed of the maxillae and
nasals with the mesethmoid and vomer. The zygomatic arch is
incomplete, and there is no trace of a separation between the orbit
and the temporal fossa. The palate is much elongated, the pterygoids
meeting in the middle line just like the palatines. The mandible is
very long and slender, there being no definite coronoid process, and a
short and slight symphysis. The hyoid arch is noticeable for the
length of the anterior cornu.
In the Armadillos (Dasypodidae) the skull varies a good deal in shape,
but the facial portion is always tapering and depressed. The zygomatic
arch is complete. In _Dasypus_ and _Chlamydophorus_ the tympanic bulla
is well ossified.
In the Glyptodontidae the skull is very short and deep; the zygomatic
arch is complete, and has a long downwardly projecting maxillary
process. The mandible is massive, and has a very high ascending
portion.
In the Manidae the skull is smooth and rounded, the zygomatic arch is
incomplete, and the orbit is inconspicuous. The palate is long and
narrow, but the pterygoids do not take part in its formation. The
mandible is slightly developed and has no angle or coronoid process.
In _Orycteropus_ the zygomatic arch is complete, and there is a small
postorbital process to the frontal. The mandible is well-developed,
having a coronoid process and definite ascending portion, and the
hyoid is well ossified.
SIRENIA. The skull, and especially the brain case of all Sirenia, is
remarkable for the general density of the component bones, which,
though often very thick, are without air sinuses. It is noticeable
also for the roughness of the bones, and the irregular manner in which
they are united together.
[Illustration FIG. 92. LATERAL VIEW OF THE SKULL OF _Rhytina stelleri_
× 1/8. (Brit. Mus.)
1. frontal.
2. parietal.
3. zygomatic process of the squamosal.
4. squamosal.
5. exoccipital.
6. occipital condyle.
7. pterygoid process of the alisphenoid.
8. jugal.
9. premaxillae.
10. angle of the mandible.
11. maxillae.]
The cranial cavity is decidedly small, the reduction being specially
noticeable in the cerebral fossa, which is not much larger than the
cerebellar fossa. The foramen magnum is large, and the dorsal surface
of the cranium narrow. The zygomatic arch is very strongly developed,
the squamosal (fig. 92, 4) being especially prominent, and being drawn
out not only into the zygomatic process, but also into a large
post-tympanic process which articulates with the exoccipital. At the
side of the skull between the squamosal, supra-occipital and
exoccipital, there is a wide vacuity in the cranial wall, partially
filled up by the very large periotic, which is ankylosed to the
tympanic, but is not united to any other bones of the skull. The
foramen lacerum medium is confluent with the foramen lacerum anterius,
and the two together form an enormous vacuity on the floor of the
skull, bounded chiefly by the exoccipital, basi-occipital, alisphenoid
and squamosal. The jugal (fig. 92, 8) is large and in _Manatus_ sends
up a strong process, which nearly or quite meets the postorbital
process of the frontal, completing the orbit. In the other Sirenia the
orbit is completely confluent with the very large temporal fossa. The
lachrymal in _Manatus_ is very small, but is larger in _Halicore_. The
premaxillae (fig. 92, 9) are large, but smaller in _Manatus_ than in
the other genera, in all of which they are curiously bent down in
front. Their upper margin forms the anterior border of a very large
aperture lying high on the roof of the skull and extending back for a
considerable distance. This aperture is formed by the union of the two
anterior nares. The nasals are quite vestigial or absent, and the
narial aperture is bounded above by the frontals; in its floor are
seen the slender vomer and large mesethmoid. The palate is long and
narrow, and formed mainly by the maxillae; behind it there is a large
irregular process formed by the union of the palatine, pterygoid, and
pterygoid plate of the alisphenoid. The mandible is very massive and
has a very high ascending portion, a rounded angle (fig. 92, 10), and
a prominent coronoid process; the two rami are firmly ankylosed
together. The hyoid consists principally of the broad flat basi-hyal;
the anterior cornua are but slightly ossified, while the thyro-hyals
are not ossified at all.
CETACEA. The skull in all Cetacea, especially in the Odontoceti, is a
good deal modified from the ordinary mammalian type.
In the _ARCHAEOCETI_ this modification is less marked than in either
of the other suborders. The nasals and premaxillae are a good deal
larger than they are in living forms, and the anterior nares are
placed further forward. The maxillae do not extend back over the
frontals, and there is a well-marked sagittal crest.
In the _MYSTACOCETI_ the skull is always quite bilaterally
symmetrical, and is not so much modified from the ordinary mammalian
type as in the Odontoceti. The parietals are not, as in the
Odontoceti, separated by a wide interparietal, but meet; they are,
however, hidden under the very large supra-occipital. The nasals are
developed to a certain extent, and the nares, though placed very far
back and near the top of the head, terminate forwardly-directed narial
passages. Turbinal bones are also developed to some extent; this fact,
and the occurrence of a definite though small olfactory fossa
constituting important distinctions from the Odontoceti. The maxillae
are large, but do not extend back to cover the frontals as in the
Odontoceti. The zygomatic process of the squamosal is very large. The
mandibular rami are not compressed, but are rounded and arched
outwards, and never meet in a long symphysis.
_ODONTOCETI._ The skull departs widely from the ordinary mammalian
type. The following description will apply to any of the following
genera of the Delphinidae, _Phocaena_, _Globicephalus_,
_Lagenorhynchus_, _Delphinus_, _Tursiops_, _Prodelphinus_, _Sotalia_.
The upper surface of the skull is more or less asymmetrical. The
cerebral cavity is high, short and broad; and formed mainly by the
cerebral fossa, the olfactory fossa being entirely absent. The
supra-occipital (fig. 93, 3) is very large, and forms much of the
posterior part of the roof of the skull. It has the interparietal
(fig. 93, 7) fused with it, and completely separates the two
parietals. The frontal (fig. 93, 10) is large and laterally expanded,
forming the roof of the orbit, but is almost completely covered by an
extension of the maxillae. The zygomatic arch is very slender, and is
mainly formed by a rod-like process from the jugal (fig. 93, 15), the
zygomatic process of the squamosal being short and stout.
The nasal passages are peculiarly modified, instead of passing
horizontally forwards above the roof of the mouth, they pass upwards
and even somewhat backwards towards the top of the skull (fig. 93,
23). They are bounded laterally by two processes from the premaxillae,
the left of which is shorter than the right. The nasal cavities are
narrow and without turbinals and the nasals (fig. 93, 19) are almost
as much reduced as in Sirenia.
[Illustration FIG. 93. A, LATERAL VIEW, AND B, LONGITUDINAL SECTION OF
THE SKULL OF A YOUNG CA'ING WHALE (_Globicephalus melas_) × 1/6.
(Brit. Mus.)
1. basi-occipital.
2. exoccipital.
3. supra-occipital.
4. basisphenoid.
5. alisphenoid.
6. parietal.
7. interparietal.
8. presphenoid.
9. orbitosphenoid.
10. frontal.
11. mesethmoid.
12. tympanic.
13. periotic.
14. squamosal.
15. jugal.
16. vomer.
17. palatine.
18. pterygoid.
19. nasal.
20. maxillae.
21. premaxillae.
22. mandible.
23. anterior nares.]
In front of the nasal openings the face is prolonged as a narrow beak
or rostrum of varying length, formed by the maxillae and premaxillae
surrounding the vomer and large mesethmoid (fig. 93, 11), which sends
forwards a long partially cartilaginous process, and is fused behind
with the presphenoid (fig. 93, 8). The basi-occipital (fig. 93, 1) too
is fused with the basisphenoid. The foramen rotundum is confluent with
the sphenoidal fissure, and the foramen ovale with the foramen lacerum
medium and the foramen lacerum posterius. The palate is mainly formed
by the maxillae; the premaxillae and palatines (fig. 93, 17), though
both meet in symphyses, forming very little of it. The pterygoids vary
in size in the different genera, sometimes as in _Lagenorhynchus_ and
_Delphinus_ meeting in the middle line, sometimes as in _Phocaena_ and
_Globicephalus_ (fig. 93, 18) being widely separated. The tympanic and
periotic are not fused together, and the periotic has generally no
bony union with the rest of the skull. The mandible is rather slightly
developed, with the rami straight, compressed and tapering to the
anterior end. The condyle is not raised at all above the edge of the
ramus; the angle is rounded and the coronoid process is very small.
_Platanista_ has a curiously modified skull; the rostrum and mandible
are exceedingly long and narrow, and arising from the maxillae are two
great plates of bone which nearly meet above.
In the Physeteridae the skull is raised into a very prominent crest at
the vertex behind the nares. In front of this in _Hyperoödon_ a pair
of ridges occur, formed by outgrowths from the maxillae. In the old
male these ridges reach an enormous size and almost meet in the middle
line. In _Physeter_, the Sperm whale, these ridges are not developed;
the maxillae and premaxillae unite with the other bones of the crest
enclosing an enormous half basin-shaped cavity, at the base of which
are the very asymmetrical anterior narial apertures.
In all living Cetacea the hyoid has the same general shape, consisting
firstly of a crescentic bone formed by the fusion of the thyro-hyals
with the basi-hyal, and secondly of the anterior cornu formed
principally by the strong stylo-hyal.
UNGULATA. None of the distinctive characters separating the Ungulata
from the other groups of mammals are drawn from the skull. But in the
Ungulata vera as opposed to the Subungulata a distinguishing feature
is found in the fact that the lachrymal and jugal form a considerable
part of the side of the face, and that the jugal always forms the
anterior part of the zygomatic arch, the maxillae taking no part in it.
UNGULATA VERA.
_ARTIODACTYLA._ The skull in Artiodactyla differs from that in
Perissodactyla in the fact that the posterior end of the nasal is not
expanded and there is no alisphenoid canal.
The skulls in the different groups of Artiodactyla differ considerably
from one another.
[Illustration FIG. 94. A, CRANIUM AND B, MANDIBLE OF A PIG (_Sus
scrofa_) × 1/5. (Camb. Mus.)
1. jugal.
2. postorbital process of the frontal.
3. zygomatic process of the squamosal.
4. supra-occipital.
5. glenoid cavity.
6. occipital condyle.
7. foramen magnum.
8. paroccipital process of the exoccipital.
9. tympanic bulla.
10. pterygoid.
11. anterior palatine foramen.
12. palatal plate of maxillae.
13. coronoid process.
14. mandibular condyle.
_i_ 1, _i_ 2, _i_ 3. first, second, and third incisors.
_c._ canine.
_pm_ 1, _pm_ 2, _pm_ 3, _pm_ 4. first, second, third, and fourth
premolars.
_m_ 1, _m_ 2, _m_ 3. first, second, and third molars.]
The skull of the Pig[166] will be described as illustrative of the
skull in the Suina. In the Pig as in most Artiodactyla the face is
bent sharply down on the basicranial axis, the commencement of the
vomer being situated below the mesethmoid instead of in front of it as
in most skulls. The occipital region of the skull is small, and the
line of junction of the supra-occipital and parietals is raised into a
prominent occipital crest. The parietal completely fuses at an early
stage with its fellow, and the exoccipital is drawn out into a long
paroccipital process (fig. 94, A, 8). The frontal is large and broad
and drawn out into a small postorbital process. The lachrymal too is
large and takes a considerable part in forming the side of the face in
front of the orbit, as does also the jugal, though to a less extent.
The face is long and tapers much anteriorly. The nasals are long and
narrow, as are the nasal processes of the premaxillae, which do not
however reach the frontals. A prenasal ossicle is developed in front
of the mesethmoid. The palate is long and narrow, the pterygoid (fig.
94, A, 10) is small, but the pterygoid process of the alisphenoid is
prominent. The squamosal is small and has the tympanic fused with it;
the tympanic is dilated below, forming a bulla (fig. 94, A, 9) filled
with cancellous bone, and above forms the floor of a long
upwardly-directed auditory meatus. The mandible has a high ascending
portion and a small coronoid process (fig. 94, B, 13). The hyoid
differs from that of most Ungulates, the stylo-hyal being very
imperfectly ossified.
[Illustration FIG. 95. MANDIBLE OF A HIPPOPOTAMUS (_H. amphibius_) ×
1/7. (Camb. Mus.)
The second incisor of the left side is missing and the crowns of the
grinding teeth are much worn.
1. condyle.
2. coronoid process.
3. mental foramina.
_i_ 1, _i_ 2. first and second incisors.
_c._ canine.
_pm_ 3. third premolar.
_m_ 1, _m_ 3. first and third molar.]
In _Hippopotamus_ the skull though essentially like that of the pig is
much modified in detail. The brain cavity is very small, while the
jaws are immensely developed. The face contracts in front of the
orbits and then expands again greatly, to lodge the enormous incisor
and canine teeth. The postorbital bar is complete or nearly so, and
the orbits project curiously outwards and slightly upwards; the
lachrymal is thin and much dilated. The squamosal is drawn out into a
postglenoid process, and the hamular process of the pterygoid is
prominent. The tympanic bulla is filled with cancellous bone. The
mandible is enormously large, the symphysis is long, the angle much
expanded and drawn out into a process which projects outwards and
forwards.
Among extinct forms related to the Suina, _Cyclopidius_ is noticeable
for having large vacuities in the lachrymo-nasal region, while
_Cotylops_ has the postorbital bar complete; both these forms are from
the North American Miocene.
In the Tylopoda and Tragulina the skull resembles in most respects
that of the Ruminants, shortly to be described; but it is allied to
that of the Suina in having the tympanic bulla filled with cancellous
bone. The tympanic bulla is better developed in the Tragulina than in
most Ungulates.
Among Ruminants, the Bovidae, that large group including the Oxen,
Sheep, and Antelopes, as a rule have the face bent on the basicranial
axis much as in the Suina. The parietals are generally small and early
coalesce, the frontals are large and are usually drawn out into horn
cores, which are however absent in the skulls of some domestic
varieties of sheep and oxen, and also in some of the earlier extinct
forms of Bovidae. These horn cores are formed internally of cancellous
bone, and on them the true epidermal horns are borne. In young animals
there is a distinct interparietal, but this early fuses with the
supra-occipital, and in the oxen also with the parietals. The
occipital crest is generally well marked, but in the genus _Bos_
becomes merged in a very prominent straight ridge running between the
two horn cores; this ridge, which contains air cells communicating
with those in the horn cores, is not nearly so well marked in _Bison_.
There is often, as in _Gazella_, a vacuity on the side of the face
between the nasal, frontal, lachrymal, and maxillae, but this is not
found in oxen or sheep. The premaxillae are small, the nasals are long
and pointed, and the turbinals are much developed. The Saiga antelope
has a curiously specialised skull; the nasals are absent or have
coalesced with the frontals and the anterior nares are enormously
large. In all Ruminants the lachrymal is large and forms a
considerable part of the side of the face; it often bears a
considerable depression, the _suborbital_ or _lachrymal fossa_, well
seen in most of the smaller antelopes. The postorbital bar is
complete, and the orbit is prominent and nearly circular. The
palatines and pterygoids are moderately large, and the pterygoids have
a backwardly-projecting hamular process. The squamosal is small, but
has a postglenoid process. The tympanic is not fused to the periotic
and has a small bulla not filled with cancellous bone. There is a
large paroccipital process to the exoccipital and the mandible has a
long slender coronoid process.
In the Cervidae and Giraffidae the face is not bent down on the
basicranial axis as it is in the Bovidae. The frontals are drawn out,
not into permanent horn cores as in the Bovidae, but into short
outgrowths, the pedicels, upon which in the Cervidae long antlers are
annually developed. These _antlers_ are outgrowths of bone, and are
covered during development by vascular integument, which dries up and
peels off when growth is complete. Every year they are detached, by a
process of absorption at the base, and shed. They may occur in both
sexes, as in the Reindeer, but as a rule they are found only in the
male. They are generally more or less branched, and are sometimes of
enormous size and weight, as in the extinct _Cervus megaceros_. In
young animals they are always simple, but become annually more and
more complicated as the animal grows older.
In the Giraffe the frontals bear a small pair of bony cores, which are
at first distinct, but subsequently become fused to the skull. In the
allied _Sivatherium_, a very large form from the Indian Pliocene, the
skull bears two pairs of bony outgrowths, a pair of short conical
outgrowths above the orbits, and a pair of large expanded outgrowths
on the occiput.
The opening of the lachrymal canal is commonly double and the
lachrymal fossa is large in the Cervidae and the Giraffidae except
_Sivatherium_. The vacuity between the frontal, lachrymal, maxillae,
and nasal is specially large.
The hyoid of Ruminants is noticeable for the development of the
anterior cornua, which include stout and short cerato-hyals and
epi-hyals, long and strong stylo-hyals and large tympano-hyals which
are more or less imbedded in the tympanics.
_PERISSODACTYLA._ In the skull of Perissodactyles an alisphenoid canal
is found and the nasals are expanded behind. Among the living animals
belonging to this group the skull least modified from the ordinary
type is that in _Rhinoceros_. In this form the skull is considerably
elongated, the facial portion being very large. The occipital region
is elevated, but the cranial cavity is small, the boundary line
between the occipital and parietal regions being drawn out into a
prominent crest, which is occupied by air cells. There is no
postorbital process to the frontal, and the orbit is completely
confluent with the temporal fossa. The nasals are fused together and
are very strongly developed, extending far forwards, sometimes
considerably beyond the premaxillae. In some extinct species, such as
_Elasmotherium_ and the Tichorhine Rhinoceros, _R. antiquitatis_, the
mesethmoid is ossified as far forwards as the end of the nasals. The
nasals are arched and bear one or two roughened surfaces to which the
great nasal horns are attached. The premaxillae are very small and the
pterygoids are slender. The palate is long, narrow, and deeply
excavated behind. The postglenoid process of the squamosal is well
developed, and generally longer than the paroccipital process of the
exoccipital. The tympanic and periotic are both small and are fused
together. The condyle of the mandible is very wide, the angle rounded,
and the coronoid process moderately developed.
In the Titanotheriidae, a family of extinct Perissodactyla from the
Miocene of North America, the occipital region is much elevated, as is
also the fronto-nasal region, the nasals (perhaps only in the male)
bearing a pair of blunt bony outgrowths. Between these two elevated
regions the skull is much depressed. The cranial cavity is very small,
the orbit confluent with the temporal fossa, and the zygomatic arch
massive.
In _Tapirus_ the orbit and temporal fossa are confluent. The nasals
are small, wide behind and pointed in front, and are supported by the
mesethmoid; the anterior nares are exceedingly large and their lateral
boundaries are entirely formed by the maxillae. The postglenoid and
post-tympanic processes of the squamosal are large. The periotic is
not fused to the squamosal or to the small tympanic. The mandible is
large and has the angle much developed and somewhat inflected.
_Palaeotherium_, which lived in early Tertiary times, has a skull much
like that of the Tapir, especially as regards the nasal bones.
In the Horse and its allies (Equidae) the facial portion of the skull
is very large as compared with the cranial portion, the nasals and
nasal cavities being specially large. In the living species of the
genus _Equus_ there is no fossa between the maxillae and lachrymal, but
it occurs in some extinct species. The lachrymal and jugal form a
considerable part of the side of the face; and the orbit though small
is complete and prominent. The postorbital bar is formed by a strong
outgrowth from the frontal, which unites with a forward extension of
the squamosal. The squamosal may extend forwards and form part of the
wall of the orbit, a very unusual feature, as in most mammals the
squamosal stops before the postorbital bar. The palate is narrow and
excavated behind as in _Rhinoceros_; the palatines take very little
part in its formation. The glenoid surface for the articulation of the
mandible is very wide. The squamosal gives rise to small postglenoid
and post-tympanic processes, and the exoccipital to a large
paroccipital process. The tympanic and periotic are ankylosed
together, but not to any other bones.
In the SUBUNGULATA, the lachrymal and jugal do not form any
considerable part of the side of the face, and the maxillae commonly
takes part in the formation of the zygomatic arch.
_TOXODONTIA._ The skull in the Toxodontia shows several Artiodactyloid
features, while the manus and pes are of a more Perissodactyloid type.
The Artiodactyloid features are (1) the absence of an alisphenoid
canal, (2) the fact that the palate is not excavated behind, and that
the palatines form a considerable part of it, and (3) the fusion of
the tympanic to the squamosal and exoccipital, forming the floor of an
upwardly directed auditory meatus. The frontal has a fairly well
developed postorbital process, but the orbit is confluent with the
temporal fossa. The premaxillae is well developed, as is the
paroccipital process of the exoccipital, especially in _Typotherium_.
The mandible has a rounded angle and a coronoid process of moderate
size. In _Typotherium_ the ascending portion is very massive.
_CONDYLARTHRA._ As far as is known the skull of these generalised
Ungulates is depressed, and is frequently marked by a strong sagittal
crest. The cranial cavity is small, the cerebral fossa in _Phenacodus_
being exceptionally small. The orbit is completely confluent with the
temporal fossa.
_HYRACOIDEA._ The skull of _Procavia_ resembles that of
Perissodactyles more than that of any other Ungulates, but differs
strongly in the comparatively small size of its facial portion. The
posterior portion of the cranium is rather high, the occipital plane
being nearly vertical. There is a small interparietal. The nasals are
wide behind, and the zygomatic arch is strongly developed, its most
anterior part being formed by the maxillae. The jugal and parietal give
rise to postorbital processes which sometimes meet, but as a rule the
orbit is confluent with the temporal fossa; it is very uncommon for
the parietal to give rise to a postorbital process, and even in
_Procavia_ the frontal often forms part of the process. The
alisphenoid canal, and postglenoid and paroccipital processes are well
developed. The tympanic bulla is large and the periotic and tympanic
are fused together, but not as a rule to the squamosal. The ascending
portion of the mandible is very high and broad, the angle rounded and
the coronoid process moderate in size. The hyoid is singular, there is
a large flat basi-hyal prolonged laterally into two broad flattened
thyro-hyals. Articulating with its anterior end are two large
triangular cerato-hyals, which are drawn out into two processes
meeting in the middle line.
_AMBLYPODA._ In the Uintatheriidae (Dinocerata) the skull has a very
remarkable character, being long and narrow and drawn out into three
pairs of rounded protuberances, a small pair on the nasals, a larger
pair on the maxillae in front of the orbits, and the largest pair on
the parietals. The cranial cavity, and especially the cerebral fossa,
is extraordinarily small. The orbit is not divided behind from the
temporal fossa. The mandible has a prominent angle, and a long curved
coronoid process; its symphysial portion bears a curious flattened
outgrowth to protect the great upper canines.
In _Coryphodon_ the skull is of a more normal character, being without
the conspicuous protuberances. The cranial cavity though very small is
not so small as in _Uintatherium_.
[Illustration FIG. 96. SKULL OF A YOUNG INDIAN ELEPHANT (_Elephas
indicus_), SEEN FROM THE RIGHT SIDE, THE ROOTS OF THE TEETH HAVE BEEN
EXPOSED. × 1/8. (Camb. Mus.)
1. exoccipital.
2. parietal.
3. frontal.
4. squamosal.
5. jugal.
6. premaxillae.
7. maxillae.
9. supra-occipital.
13. basi-occipital.
14. postorbital process of the frontal.
15. lachrymal.
16. pterygoid process of the alisphenoid.
_i_ 1. incisor.
_mm_ 3., _mm_ 4. third and fourth milk molars.
_m_ 1. first molar.]
_PROBOSCIDEA._ The character of the skull in the young elephant
differs much from that in the old animal. In very young individuals
the skull is of a normal character, and the cranial cavity is
distinctly large in proportion to the bulk of the skull. But as the
animal gets older, while its brain does not grow much, the size of its
trunk and especially of its tusks increases greatly; and consequently
the skull wall is required to be of very great superficial extent in
order to afford space for the attachment of the muscles necessary for
the support of these heavy weights. This increase in superficial
extent is brought about without much increase in weight of bone by the
development of an enormous number of air cells in nearly all the bones
of the skull; sometimes, as in the case of the frontal, separating the
inner wall of the bone from the outer, by as much as a foot. This
development of air cells is accompanied by the obliteration of the
sutures between the various bones. The most noticeable point with
regard to the cranial cavity is the comparatively large size of the
olfactory fossa. The supra-occipital (figs. 96 and 97, 9) is
large--exceedingly large in the adult skull; the parietals (figs. 96
and 97, 2) are also very large. The frontals send out small
postorbital processes, but these do not meet processes from the small
jugal, which forms only the middle part of the slender zygomatic
arch, the anterior part being formed by the maxillae. The lachrymal
(fig. 96, 15) is small and lies almost entirely inside the orbit. The
anterior narial aperture (fig. 97, 8) is wide and directed upwards,
opening high on the anterior surface of the skull. It is bounded above
by the short thick nasals and below by the premaxillae. The narial
passage is freely open, maxillo-turbinals not being developed. The
palatine is well developed, the pterygoid is small and early fuses
with the pterygoid process of the alisphenoid. The tympanic is united
with the periotic but not with the squamosal, and forms a large
auditory bulla. There are no paroccipital or postglenoid processes.
The exoccipital is not perforated by the condylar foramen,--a very
exceptional condition.
[Illustration FIG. 97. LONGITUDINAL SECTION TAKEN RATHER TO THE RIGHT
OF THE MIDDLE LINE OF THE SKULL OF A YOUNG INDIAN ELEPHANT (_E.
Indicus_) × 1/8. (Camb. Mus.)
8. anterior nares.
10. periotic.
11. palatine.
12. pterygoid.
17. nasal.
Other numbers as in Fig. 96.]
The mandible has a high ascending portion, is rounded off below and
has no angle. The symphysial portion is long, narrow, and spout-like,
and the coronoid process is small. The thyro-hyals are ankylosed with
the basi-hyal, which is connected with the large forked stylo-hyals by
ligament only.
RODENTIA. The cranial cavity is depressed, elongated, and rather
small, and the cerebral fossa lies entirely in front of the cerebellar
fossa. The occipital plane is vertical or directed somewhat backwards,
and the supra-occipital does not form much of the roof of the cranium.
The paroccipital processes of the exoccipitals are generally of
moderate size; in the Capybara (_Hydrochaerus_), however, they are
very long, and are laterally compressed and directed forwards. The
parietals are small, and often become completely fused together; there
is sometimes a small interparietal. The frontals in most genera have
no trace of a postorbital process; in Squirrels, Marmots and Hares,
however, one occurs, but in no case does it meet a corresponding
process from the zygomatic arch, so the orbit and temporal fossa are
completely confluent. In Hares the postorbital process of the frontal
is much flattened, and has an irregular margin. The temporal fossa is
always small, and in _Lophiomys_ is arched over by plates arising
respectively from the parietal and jugal; a secondary roof is thus
partially developed in a manner unique among mammals, but carried to a
great extent in many Chelonia. The nasal bones and cavities are large,
attaining their maximum development in the Porcupines (fig. 98, 1).
The premaxillae is always very large, and sends back a long process
which meets the frontal. The vomer is occasionally found persisting in
two separate halves, a feature recalling the arrangement in
Sauropsids. In many Rodents there is an enormous vacuity at the base
of the maxillary portion of the zygomatic arch. It is sometimes as
large as the orbit, and attains its maximum development in the
Capybara and other Hystricomorpha; in the Marmots, Beavers, and
Squirrels (Sciuromorpha), and in the Hares it is undeveloped. In
_Lagostomus_ the maxillae bears an upwardly directed plate of bone,
shutting off from this vacuity a space which is the true infra-orbital
foramen.
[Illustration FIG. 98. HALF FRONT VIEW OF THE SKULL OF A PORCUPINE
(_Hystrix cristata_) × 1/2. (Camb. Mus.)
1. nasal.
2. maxillo-turbinals.
3. infra-orbital vacuity.
4. maxillae.
5. premaxillae.
6. jugal.
_i_ 1. upper incisor.]
The zygomatic arch is always complete, and in many cases the jugal
extends back to form part at least of the glenoid surface for
articulation with the mandible. In _Coelogenys_ the jugal and
maxillary portion of the zygomatic arch is greatly expanded and
roughened, and the maxillary portion encloses a large cavity. The
palate in Rodents is narrow, and the space between the incisor and
molar teeth passes imperceptibly into the sides of the face. The
anterior palatine foramina form long, rather narrow slits in this
region. The bony palate between the grinding teeth is sometimes as in
the Hares very short, sometimes as in the Capybara very long. The
maxillae extends back beneath the orbit to unite with the squamosal.
The pterygoid is always small, but sometimes has a well-marked hamular
process which in _Hystrix_, _Lagostomus_, and some other genera unites
with the tympanic bulla. The periotic is large, and fused with the
tympanic, which forms a prominent bulla, and is generally drawn out
into a tubular meatus. The bulla attains its maximum development in
_Chinchilla_ and _Dipus_.
The mandible is narrow and rounded in front, the two halves meeting in
a long symphysis. The angle is generally drawn out into a long
backwardly-projecting process, which is often pointed and directed
upwards. In the Hares the angle is rounded. The coronoid process is
never large.
There are a number of points in which the skull of the Duplicidentata
(Hares and Rabbits) differs from that of other Rodents. (_a_) The
sutures between the basi-occipital and basisphenoid, and between the
basisphenoid and presphenoid remain open throughout life. (_b_) Much
of the maxillae forming the side of the face in front of the orbit is
fenestrated. (_c_) The optic foramina are united to form a single
hole, much as in birds. (_d_) The coronoid process is slightly
differentiated from the ascending portion of the mandible. The first
two of these points have been thought to indicate degradation of the
hares and rabbits as compared with higher mammals.
CARNIVORA[167]. It is characteristic of the skull in Carnivora that
the glenoid fossa is deep, and the postglenoid process (fig. 75, 23)
well developed. The condyle of the mandible is much elongated
transversely. The orbit and temporal fossa in the great majority of
forms communicate freely, the postorbital bar being incomplete.
_CARNIVORA VERA._ The axis of the facial portion of the skull is a
direct continuation of that of the cranial portion. The cranial
cavity though rather depressed is large, and generally long, though in
Cats it is comparatively short and wide. The occipital plane is nearly
vertical, and the exoccipitals are developed into fairly prominent
paroccipital processes. The interparietal is commonly distinct, and
the parietals unite in a long sagittal suture, which is often
developed into a crest. The nasals (fig. 73, 4) are well developed,
especially in Cats, and the nasal processes of the premaxillae do not
nearly reach the frontals. A considerable part of the palate is formed
by the palatine, and the maxillary portion is pierced by rather long
anterior palatine foramina. The pterygoid has a hamular process. The
zygomatic arch is strong, especially in Cats. Postorbital processes
are developed on the frontal (fig. 73, 10) and jugal, but never form a
complete postorbital bar. A carotid canal is well seen in the Ursidae,
and to a less extent in the Felidae; in the Canidae there is an
alisphenoid canal (fig. 75, 21).
The auditory bulla differs a good deal in the different groups. In the
Bears (Ursidae) it is not much inflated, and is most prominent along
its inner border; it is not closely connected with the paroccipital
process. In the Cats it is very prominent, and its cavity is almost
divided by a septum into two parts, the inner of which contains the
auditory ossicles. The paroccipital process is closely applied to the
bulla. In the Dogs the bulla is intermediate in character between that
of the Cats and that of the Bears; it is partially divided by a
septum, and is moderately expanded.
The mandible is well developed with a prominent angle (fig. 72, 26),
and a large coronoid process. The hyoid consists of a broad basi-hyal,
a long many-jointed anterior cornu and short thyro-hyals (fig. 72,
33).
The skull in the _CREODONTA_ is in most respects allied to that of the
Canidae, but presents some ursine affinities. The tympanic bulla is
fairly prominent, but has no well-developed septum. The cranial cavity
is very small and narrow, the zygomatic arch standing away from it.
The temporal fossa is of great size.
In the _PINNIPEDIA_ the cranial cavity is large and rounded. The skull
is much compressed in the interorbital region, and in correlation with
this compression the ethmo-turbinals are little developed, while the
maxillo-turbinals are large. The orbit is large, and the temporal
fossa smaller than in the Carnivora vera. In the Walrus (_Trichechus_)
the anterior part of the face is distorted by the development of the
huge canines. The Otariidae have an alisphenoid canal. The tympanic
bulla is small in _Otaria_, large in the Phocidae, and flattened in
the Walrus. The hyoid is similar to that in Carnivora vera.
INSECTIVORA. The skull varies much in the different members of the
order Insectivora, but the following points of agreement are found.
The cranial cavity is of small size, and is never much elevated. The
facial part of the skull is generally considerably elongated, and the
nasals and premaxillae are well developed. The zygomatic arch is
usually slender or incomplete, and the coronoid process and angle of
the mandible are commonly prominent.
In some Insectivora, such as _Galeopithecus_, _Tupaia_, and
_Macroscelides_, the skull shows a higher type of structure than is
met with in most members of the order. In these genera the cranial
cavity is comparatively large, and the occipital plane is nearly
vertical. The zygomatic arch is fairly strong, and the frontal and
jugal give rise to postorbital processes which nearly or quite
(_Tupaia_) meet. The tympanic bulla is well developed, and produced
into a tubular auditory meatus, this being specially well marked in
_Macroscelides_.
In the other Insectivora the cranial cavity is of smaller comparative
size, and the orbit and temporal fossa are completely confluent, often
without any trace of a postorbital bar. The occipital plane commonly
slopes forwards. In the Hedgehogs (Erinaceidae) and Centetidae the
tympanic is very slightly developed, forming a small ring. The
zygomatic arch of Hedgehogs and _Gymnura_ is very slender, the jugal
being but little developed and the squamosal and maxillae meeting one
another; in the Centetidae the jugal is absent and the arch is
incomplete.
The Moles (Talpidae) have an elongated, depressed and rounded skull
with a very slender zygomatic arch formed by the squamosal and
maxillae. The nasals are fused together, and the mesethmoid is ossified
very far forwards. In the Shrews (Soricidae) there is no zygomatic
arch; the tympanic is ring-like, and the angle of the mandible is very
prominent. The hyoid has a transversely extended basi-hyal, a long
anterior cornu with three ossifications, and thyro-hyals which are
sometimes fused to the basi-hyal.
CHIROPTERA. In the frugivorous Flying Foxes (Pteropidae) the skull is
elongated, and the cranial cavity is large and arched, though
considerably contracted in front. There are commonly strong sagittal
and supra-orbital crests. The parietals take a great part in the
formation of the walls of the cranial cavity, the supra-occipital and
frontals being small. The frontal is drawn out into a long postorbital
process, but the zygomatic arch, which is slender, and formed mainly
by the squamosal and maxillae, gives rise to only a small postorbital
process, so that the orbit and temporal fossa are confluent. There is
no alisphenoid canal, and the tympanics are very slightly connected
with the rest of the skull. The mandible has a large coronoid process,
a rounded angle, and a transversely expanded condyle.
In Insectivorous Bats the skull is generally shorter and broader than
in the Pteropidae. The cranial cavity is large and rounded, and has
thin smooth walls. The zygomatic arch is slender, and postorbital
processes are not generally well developed. The premaxillae is
generally small, sometimes absent. The tympanics are ring-like and are
not connected with the surrounding bones. The angle of the mandible is
distinct. The hyoid in most respects resembles that of the
Insectivora.
PRIMATES. The characters of the skull differ greatly in the two
suborders of Primates, the Anthropoidea and the Lemuroidea.
In the _LEMUROIDEA_ the general relative proportions of the cranium
and face are much as in most lower mammals, and the occipital plane
forms nearly a right angle with the basicranial axis. The postorbital
processes of the frontals are commonly continued as a pair of ridges
crossing the roof of the cranium and meeting the occipital crest.
Though the postorbital bar is complete, the orbit and temporal fossa
communicate freely below it. The lachrymal canal opens outside the
orbit, and the lachrymal forms a considerable part of the side of the
face. The tympanic is developed into a large bulla. The hyoid
apparatus much resembles that of the Dog.
In the _ANTHROPOIDEA_ the skull differs greatly from that in the
Lemuroidea. The cranial portion of the skull is very large as compared
with the facial portion, though the comparative development varies,
some monkeys, such as the baboons (Cynocephali) having the facial
portion relatively large. The comparative size of the jaws does not
vary inversely with the general development of the animal, some of the
Cercopithecidae having comparatively larger jaws than some of the
Cebidae. The great size of the cranial part of the skull is mainly due
to the immense development of the cerebral fossa, which commonly
completely overlaps the olfactory fossa in front, and the cerebellar
fossa behind. This development also has the effect of making the
ethmoidal and occipital planes lie, not at right angles to the
basicranial axis, but almost in the same straight line with it. This
is, however, not always the case, as the Howling Monkey (_Mycetes_)
and also some of the very highest monkeys, the Gibbons (_Hylobates_),
have the occipital plane nearly vertical to the basicranial axis. In
adult Man the basi-occipital, exoccipitals and supra-occipital
coalesce, forming the so-called occipital bone; while the
basisphenoid, presphenoid, alisphenoids, orbitosphenoids and
pterygoids form the sphenoid bone. The roof of the skull is partly
formed by the large supra-occipital and frontals, but mainly by the
parietals (fig. 99, 1), which in Man are of enormous extent.
[Illustration FIG. 99. HALF FRONT VIEW OF THE SKULLS, _A_ OF AN OLD,
_B_ OF A YOUNG GORILLA (_Gorilla savagei_) × 1/4. (Camb. Mus.)
1. parietal.
2. sagittal crest.
3. frontal.
4. supra-orbital ridge.
5. squamosal.
6. maxillae.
7. external auditory meatus.]
In Man and in most monkeys, at any rate when young (fig. 99, B), the
roof of the skull is smooth and rounded, but in many forms, such as
the Baboons, in the adult the supra-orbital and occipital ridges are
much developed. In the Gorilla this is also the case with the sagittal
crest (fig. 99, A, 2). The bones of the upper surface of the cranium
interlock with wavy outlines. The nasals vary much in length, being
much shorter in man than in most monkeys; they commonly become early
fused together, as do also the frontals. The vomer is well developed,
and the ethmo-turbinal always forms part of the boundary of the orbit.
There are frequently, as in many Lemuroidea, a pair of more or less
well-marked ridges, crossing the roof of the skull from the
postorbital processes of the frontals to the occipital crest. The
orbit is completely encircled by bone, and the alisphenoid assists the
jugal and frontal in shutting it off from the temporal fossa, leaving
however a communication between the two as the sphenomaxillary
fissure. In most cases the frontals meet one another in the middle
line between the mesethmoid and orbitosphenoid, but in Man, Simia, and
some Cebidae this does not take place. In nearly all Cebidae the
parietal and jugal meet one another, separating the frontal and
alisphenoid on the skull wall; in Man and all Old World monkeys, on
the other hand, the alisphenoid and frontal meet and separate the
jugal and parietal. The premaxillae nearly always send back processes
which meet the nasals. The palate is rather short and both the
palatine and the premaxillae take a considerable part in its formation.
The pterygoid plate of the alisphenoid is decidedly large, and there
is no alisphenoid canal. There is never any great development either
of the paroccipital process of the exoccipital, or of the postglenoid
process of the squamosal. The periotic and tympanic are always fused
together; in Cebidae they form a small bulla, but a bulla is not
developed in any Old World forms. The periotic is large, especially
the mastoid portion, which forms a distinct portion of the skull wall
between the squamosal and exoccipital. In Man and still more in Old
World monkeys, the external auditory meatus is drawn out into a
definite tube, whose lower wall is formed by the tympanic; in the
Cebidae the tympanic is ring-like. The perforation of the periotic by
the carotid canal is always conspicuous.
The mandible is rather short and broad, and the angle formed by the
meeting of the two rami is more obtuse than in most mammals. The
coronoid process is fairly well developed, and the angle is more or
less rounded. In most Primates the condyle is considerably widened,
but this is not the case in Man. In _Mycetes_ the mandible is very
large, its ascending portions being specially developed. The hyoid of
Primates is remarkable for the large expanded basi-hyal, which is
generally concave above and convex below. The anterior cornu is never
well ossified, but the thyro-hyal is always strong. In _Mycetes_ the
basi-hyal is enormously large, forming a somewhat globular thin-walled
capsule.
AUDITORY OSSICLES.
[Illustration FIG. 100. MALLEUS, STAPES AND INCUS OF _A._ MAN. _B._
DOG. _C._ RABBIT. (After DORAN) x 1.
1. head of malleus.
2. canal of stapes.
3. incus.
4. processus longus (or gracilis).
5. manubrium of malleus.
6. processus brevis.
7. lamella.]
There are in mammals four auditory ossicles forming a chain extending
from the fenestra ovalis to the tympanic membrane. Three of these, the
=malleus=, =incus= and =stapes=, are always distinct, while the
fourth, the =lenticular=, is smaller than the others and is sometimes
not distinct. The names are derived from human anatomy and indicate in
the case of the first three a more or less fanciful resemblance
respectively to a hammer, an anvil and a stirrup. The ossicles are
homologous as a whole to the hyomandibular of fishes and to the
columellar chain of Sauropsids and Amphibians. The malleus is
homologous to the extra-columella of Crocodiles and the stapes to the
columella. The =malleus= when typically developed consists of a
rounded _head_ (fig. 100, 1) which bears a surface articulating with
the incus, and a short _neck_ continued into a process, the
_manubrium_ (fig. 100, 5), which comes into relation with the tympanic
membrane. From the junction of the neck and manubrium two processes
are given off, a _processus longus_ or _gracilis_ (fig. 100, 4), which
in the embryo is continuous with Meckel's cartilage, and a _processus
brevis_ (fig. 100, 6). The =incus= generally consists of a more or
less anvil-shaped portion which articulates with the malleus, and of a
process which is connected with the stapes by the small =lenticular=.
The =stapes= is generally stirrup shaped, consisting of a basal
portion from which arise two _crura_ separated by a space the canal
through which a branch of the pharyngeal artery runs The lenticular is
frequently cartilaginous and sometimes is not developed at all.
The above is the arrangement of the auditory ossicles met with in the
higher Mammalia, but in the lower Mammalia the characters approach
more nearly to those met with in Sauropsids.
In MONOTREMES the ossicles, though distinctly mammalian in character,
show a very low type of development. The incus is articulated, or
often fused, with an outgrowth from the head of the malleus. The
stapes is very much like a reptilian columella, having a single crus
with no perforation.
In MARSUPIALS the ossicles are of a low type, but not so low as the
rest of the skeleton might have led one to expect, and all or almost
all the points showing a low grade of development may be paralleled
among the Monodelphia. The lowest Marsupials as regards the ossicles
are the Peramelidae, whose ossicles are of a frail papery consistence.
The Didelphyidae on the other hand have the most highly developed
ossicles, the malleus much resembling that of many Insectivores, and
the stapes having two definite crura separated by a canal.
In EDENTATES the character of the ossicles varies much. In Sloths the
stapes approaches that of Sauropsids in its narrowness and the slight
trace of a canal; this character is however still more marked in
_Manis_, whose stapes is as Sauropsidan as that of Monotremes, and
consists of a nearly circular basal plate bearing a column which does
not show any sign of division into crura. The stapes of other
Edentates, such as ant-eaters, aard varks, and most armadillos, is of
a high type and has well-developed crura. _Priodon_ has a lower type
of stapes than _Dasypus_ and _Tatusia_.
The ossicles of the SIRENIA differ widely from those of all other
mammals in their great density and clumsy form.
In CETACEA the ossicles are solid, though not so solid as in Sirenia,
and their details vary much. The malleus is always firmly fused to the
tympanic by means of the processus longus, and the manubrium is very
little if at all developed. The incus has the stapedial end greatly
developed, and the stapes has very thick crura with hardly any canal.
The ossicles of the Mystacoceti are apparently less specialised than
are those of the Odontoceti.
The auditory ossicles of the UNGULATA do not present any characters
common to all the members of the group.
Among Ruminants they are chiefly remarkable for the development of a
broad lamellar expansion between the head and the processus longus of
the malleus. In some cases the malleus of the foetus differs
strikingly from that of the adult. Among Perissodactyla the Rhinoceros
and Tapir have the malleus of a low type, recalling those of
Marsupials; while in the Horse the head is well developed, and the
malleus is of a higher type.
The ossicles of _Procavia_, which recall those of the Equidae, are
chiefly remarkable for the small size of the body of the incus. In
Elephants the ossicles are large and massive.
In the RODENTIA (fig. 100, C) the malleus is generally characterised
by a very broad manubrium. In many genera such as _Bathyergus_, and
most of the Hystricomorpha such as _Hystrix_, _Chinchilla_ and
_Dasyprocta_, the malleus and incus are ankylosed together.
CARNIVORA. In Carnivora vera the most striking feature of the malleus
is the occurrence of a broad lamellar expansion between the head and
neck and the processus longus. This however does not occur in some
Viverridae. In the Carnivora vera the incus and stapes are small as
compared with the malleus, but in the Pinnipedia they are large. In
the Pinnipedia the auditory ossicles have a very dense consistence,
and except in the Otariidae are very large. The stapes frequently has
no canal, or only a very small one.
In INSECTIVORA the characters of the auditory ossicles are very
diverse. Many forms such as shrews, moles, hedgehogs, and the
Centetidae have a low type of malleus resembling that of Edentates.
_Chrysochloris_ has very extraordinary auditory ossicles. The head of
the malleus is drawn out into a great club-shaped process, the incus
is long and narrow, and differs much from the ordinary type.
In CHIROPTERA the ossicles and especially the malleus much resemble
those of shrews. The stapes is always normal in character, never
becoming at all columelliform.
PRIMATES. In Man and the Anthropoid Apes the malleus has a rounded
head, a short neck, and the manubrium, a processus longus and a
processus brevis. The incus consists of an anvil-shaped portion from
which arises a long tapering process. The stapes has diverging crura
and consequently a wide canal. The crura in other monkeys do not
diverge so much as in man and anthropoid apes. The New World monkeys
have no neck to the malleus.
THE STERNUM[168].
In MONOTREMES and most MARSUPIALS the sternum does not present any
characters of special importance. The presternum is strongly keeled in
_Notoryctes_.
The sternum in EDENTATES is very variable: in the Sloths it is very
long, the mesosternum of _Choloepus_ having twelve segments. In the
ant-eaters and armadillos the presternum is broad and sometimes as in
_Priodon_ strongly keeled. In _Manis macrura_ the xiphisternum is
drawn out into a pair of cartilaginous processes about nine inches
long.
In the SIRENIA the sternum is simple and elongated, and of fairly
equal width throughout, in the adult it shows no sign of segmentation.
Its origin from the union of two lateral portions can be well seen in
_Manatus_.
Two distinct types of sternum are met with in the CETACEA. In the
Odontoceti the sternum consists of a broad presternum followed by
three or four mesosternal segments, but with no xiphisternum.
Indications of the original median fissure can be traced, and are very
evident in _Hyperoödon_. In the Mystacoceti, on the other hand, the
sternum consists simply of a broad flattened presternum which is
sometimes more or less heart-shaped, sometimes cross-shaped. Only a
single pair of ribs are united to it.
The sternum in UNGULATA is generally long and narrow and formed of six
or generally seven segments. The presternum is as a rule small and
compressed, often much keeled, especially in the horse and tapir. The
segments of the mesosternum gradually widen as followed back and the
xiphisternum is often terminated by a cartilaginous plate.
In the RODENTIA the sternum is long and narrow and generally has a
large presternum, and a xiphisternum terminated by a broad
cartilaginous plate.
In the CARNIVORA, too, the sternum (fig. 76) is long and narrow and
formed of eight or nine pieces, all of nearly the same size. The
xiphisternum generally ends in an expanded plate of cartilage.
In INSECTIVORA the sternum is well developed but variable. The
presternum is commonly large and is sometimes as in the Hedgehog
(_Erinaceus_) bilobed in front, sometimes as in the Shrew (_Sorex_)
trilobed. It is especially large in the Mole (_Talpa_) and is expanded
laterally and keeled below.
In the CHIROPTERA the presternum is strongly keeled and so is
sometimes the mesosternum.
Among PRIMATES, in Man and the Anthropoid Apes the sternum is rather
broad and flattened; the mesosternum consists of four segments which
are commonly fused together and the xiphisternum is imperfectly
ossified.
THE RIBS.
Free ribs are borne as a rule only by the thoracic vertebrae; ribs may
be found in other regions, especially the cervical and sacral, but
these are almost always ankylosed to the vertebrae. As a general rule
the first thoracic rib joins the presternum, while the succeeding ones
are attached between the several segments of the mesosternum. Some of
the posterior ribs frequently do not reach the sternum; they may then
be attached by fibrous tissue to the ribs in front, or may end freely
(_floating ribs_). There are generally thirteen pairs of ribs, and in
no case do they have uncinate processes.
In MONOTREMES (fig. 102, B) each rib is divided not into two but into
three parts, an intermediate portion being interposed between the
vertebral and sternal parts. The sternal ribs are well ossified, and
some are very broad and flat. The intermediate portions are
unossified, those of the anterior ribs are short and narrow, but they
become longer and wider further back.
In MARSUPIALS there are almost always thirteen pairs of ribs, whose
sternal portions are very imperfectly ossified. _Notoryctes_ has
fourteen pairs of ribs, eight of which are floating: the first rib is
very stout, and is abruptly bent on itself to join the sternum. It has
no distinct sternal portion. All the other ribs are slender.
Of the EDENTATES the Sloths have very numerous ribs; twenty-four pairs
occur in _Choloepus_, and half of these reach the sternum. In the
Armadillos there are only ten or twelve pairs of ribs, but the sternal
portions are very strongly ossified. The first rib is remarkably broad
and flat, and is not divisible into vertebral and sternal portions.
In the SIRENIA there are a very large number of ribs noticeable for
their great thickness and solidity, but not more than three are
attached to the sternum.
CETACEA. In the Whalebone whales the ribs are remarkable for their
very loose connection both with the vertebral column and with the
sternum. The capitula are scarcely developed, and the attachment of
the tubercula to the transverse processes is loose. The first rib is
the only one connected with the sternum. In the Toothed whales the
anterior ribs have capitula articulating with the centra, as well as
tubercula articulating with the transverse processes; in the posterior
ones, however, only the tubercula remain. Seven pairs of well-ossified
sternal ribs generally meet the sternum. In the Physeteridae most of
the ribs are connected to the vertebrae by both capitula and
tubercula.
In the UNGULATA the ribs are generally broad and flattened, and this
is especially the case in the genera _Bos_ and _Bubalus_ (fig. 101,
6). The anterior ribs are short and nearly straight, and sternal ribs
are well developed. The Artiodactyla have twelve to fifteen pairs of
ribs, the Perissodactyla eighteen or nineteen, and _Procavia_ twenty
to twenty-two. The Elephant has nineteen to twenty-one pairs, seven of
which may be floating ribs.
[Illustration FIG. 101. SKELETON OF A CAPE BUFFALO (_Bubalus caffer_).
The left scapula is omitted for the sake of clearness × 1/17. (Brit.
Mus.)
1. premaxillae.
2. nasal.
3. orbit.
4. neural spine of first thoracic vertebra.
5. scapula.
6. rib.
7. femur.
8. patella.
9. tibia.
10. metatarsals.
11. radius.
12. metacarpals.]
In the RODENTIA there are generally thirteen pairs of ribs, which do
not present any marked peculiarities.
The CARNIVORA have thirteen to fifteen pairs of ribs, whose vertebral
portions are slender, nearly straight and subcylindrical, while their
sternal portions are long and imperfectly ossified (fig. 76, 5). There
is nothing that calls for special remark about the ribs, in either
INSECTIVORA or CHIROPTERA.
PRIMATES. In Man and the Orang (_Simia_) there are generally twelve
pairs of ribs; in the Gorilla and Chimpanzee (_Anthropopithecus_), and
Gibbons (_Hylobates_), there are thirteen, in the Cebidae twelve to
fifteen, and in the Lemuroidea twelve to seventeen pairs. The first
vertebral rib is shorter than the others, and the sternal ribs
generally remain cartilaginous throughout life, though in man the
first may ossify.
APPENDICULAR SKELETON.
THE PECTORAL GIRDLE.
By far the most primitive type of the pectoral or shoulder girdle is
found in the MONOTREMATA. The scapula (fig. 102, A, 1) is long and
recurved, and has only two surfaces, one corresponding to the
prescapular[1] fossa, the other to the postscapular[1] and
subscapular[169] fossae. The coracoid is a short bone attached above
to the scapula and below to the presternum; it forms a large part of
the glenoid cavity. In front of the coracoid there is a fairly large
flattened epicoracoid (fig. 102, 6); there is also a large =T=-shaped
interclavicle (fig. 102, 4), which is expanded behind and rests on the
presternum. The clavicles rest on and are firmly united to the
anterior border of the interclavicle. This shoulder girdle differs
greatly from that of any other mammals, and recalls that of some
Lacertilia.
[Illustration FIG. 102. _A_, SIDE VIEW, _B_, DORSAL VIEW OF THE
SHOULDER GIRDLE AND PART OR THE STERNUM OF THE SPINY ANTEATER
(_Echidna aculeata_) × 1. (After PARKER.)
1. scapula.
2. suprascapula.
3. clavicle.
4. interclavicle.
5. coracoid.
6. epicoracoid.
7. glenoid cavity.
8. presternum.
9. second sternal rib.
10. second vertebral rib.]
In MARSUPIALS, as in all mammals except the Monotremes, the shoulder
girdle is much reduced; there are no epicoracoids and interclavicle,
and the coracoid forms simply a small process on the scapula,
ossifying from a centre separate from that giving rise to the rest of
the bone. The scapula has a long acromion, and a clavicle is always
present except in _Perameles_. Unossified remains of the precoracoids
are found at either end of the clavicle. The scapula of _Notoryctes_
has a very high overhanging spine, and there is a second strong ridge
running along the proximal part of the glenoid border.
The shoulder girdle of the EDENTATA shows some very curious
variations. In _Orycteropus_ the scapula is of very normal form and
the clavicle is well developed. In the Pangolins and Anteaters the
scapula is very broad and rounded; there is no clavicle in the
Pangolins, and generally only a vestigial one in Anteaters. In
Armadillos, Sloths, and Megatheriidae, the acromion is very long and
the clavicle is well developed. In the Sloths, _Megatherium_, and
_Myrmecophaga_, a connection is formed between the coracoid, which is
unusually large, and the coracoid border of the scapula, converting
the coraco-scapula notch into a foramen. In _Bradypus_ the clavicle is
very small, and is attached to the coracoid, which sometimes forms a
distinct bone[170].
In the SIRENIA the scapula is somewhat narrow and curved backwards:
the spine, acromion, and coracoid process are moderately developed,
and there is no clavicle.
CETACEA. In nearly all the Odontoceti the scapula is broad and
somewhat fan-shaped; the prescapular fossa is much reduced, and the
acromion and coracoid process form flattened processes, extending
forwards nearly parallel to one another. Some of the Mystacoceti, such
as _Balaenoptera_, have a broad, fan-shaped scapula, with a long
acromion and coracoid process, extending parallel to one another.
Others, such as _Balaena_, have a higher and narrower scapula, with a
smaller coracoid process.
In UNGULATA the scapula is always high and rather narrow, and neither
acromion nor coracoid process is ever much developed. In no adult
Ungulate except _Typotherium_ is there any trace of a clavicle, but a
vestigial clavicle has been described in early embryos of sheep[171].
[Illustration FIG. 103. SKELETON OF A LLAMA (_Auchenia glama_) × 1/18.
(Brit. Mus.)
1. hyoid.
2. atlas vertebra.
3. seventh cervical vertebra.
4. scapula.
5. imperfectly ossified suprascapula.
6. olecranon process of ulna.
7. metacarpals.
8. ilium.
9. patella.
10. calcaneum.]
UNGULATA VERA. In the Ruminantia the suprascapular region (fig. 103,
5) is very imperfectly ossified, and when this is removed the upper
border of the scapula is very straight (fig. 101, 5). The spine is
prominent, and generally has a fairly well-marked acromion. In
_Hippopotamus_ the acromion is fairly prominent, but in the other
Suina, though the spine is prominent, the acromion is not developed.
The Perissodactyla have no acromion, but while the Equidae and
_Hyracotherium_ have the scapula long and slender, with the spine very
slightly developed, the other living Perissodactyla have the spine
prominent and strongly bent back at about the middle of its length.
SUBUNGULATA. _Typotherium_ (Toxodontia) differs from all other known
Ungulates in having well-developed clavicles; its scapula has a strong
backwardly-projecting process, much like that in _Rhinoceros_.
_Phenacodus_ (Condylarthra), has a curiously rounded scapula, with the
coracoid and suprascapular borders passing imperceptibly into one
another. The scapula resembles that of a carnivore more than does that
of any existing Ungulate.
_Procavia_ has a triangular scapula with a prominent spine and no
acromion; there is a large unossified suprascapular region.
The scapula in the Proboscidea has a large rounded suprascapular
border and a narrow, slightly concave glenoid border. The spine is
large, and has a prominent process projecting backwards from about its
middle. The spine lies towards the front end of the scapula, so that
the postscapular fossa is much larger than the prescapular fossa.
In RODENTIA the shoulder girdle is of a rather primitive type. The
scapula is generally high and narrow, somewhat as in Ruminantia; it
differs, however, from the Ruminant scapula in having a high acromion,
which is often, as in the Hares and Rabbits, terminated by a long
metacromion. The development of the clavicle varies, and sometimes it
is altogether absent. It is frequently connected by cartilaginous
bands or ligaments (fig. 104, 7 and 9), on the one hand with the
scapula, and on the other with the sternum. These unossified bands are
remains of the precoracoid. Epicoracoidal vestiges of the sternal ends
of the coracoids (fig. 104, 11) are also often present.
In the CARNIVORA VERA the scapula is large, and generally has rather
rounded borders. The spine and acromion are well developed, and the
prescapular and postscapular fossae are nearly equal in size. The
coracoid is very small, and the clavicle is never completely
developed, being often absent, as in the Bears and most of their
allies. In the Seals (Phocidae) the scapula is elongated and curved
backwards, and has a very concave glenoid border. In the Eared Seals
(Otariidae) the scapula is proportionally much larger and wider, the
prescapular fossa being specially large, and being traversed by a
ridge, which converges to meet the spine.
[Illustration FIG. 104. DORSAL VIEW OF THE STERNUM AND RIGHT HALF OF
THE SHOULDER-GIRDLE OF _Mus sylvaticus_ × 4. (After PARKER.)
1. postscapular fossa.
2. prescapular fossa.
3. spine.
4. suprascapular border unossified.
5. coracoid process.
6. acromion.
7. cartilaginous vestige of precoracoid at scapular end of clavicle.
8. clavicle.
9. cartilaginous vestige of precoracoid at sternal end of clavicle.
10. omosternum.
11. epicoracoid.
12. presternum.
13. first segment of mesosternum.
14. xiphisternum.
15. cartilaginous termination of xiphisternum.
16. 2nd sternal rib.
17. 1st vertebral rib.]
In the INSECTIVORA the shoulder girdle is well developed and, as in
Rodents, remains are met with of various parts not generally seen in
mammals. In the Shrews the scapula is long and narrow, and has a
well-marked spine, whose end bifurcates, forming the acromion and
metacromion. The clavicle is long and slender, and is connected with
the sternum and acromion by vestiges of the precoracoid. Considerable
remains of the sternal end of the coracoid are also found. In
_Potamogale_, however, there are no clavicles. In the Mole the
shoulder girdle is greatly developed, and of very remarkable form. The
scapula is high and very narrow, with the spine and acromion very
little developed. The other shoulder girdle element is an irregular
bone, which articulates with the humerus and presternum, and is
connected by ligaments with the scapula. This bone appears to
represent both the coracoid and the clavicle, being formed partly of
cartilage bone, partly of membrane bone.
In the CHIROPTERA the scapula is large and oval, and has a moderately
high spine and a large acromion. The coracoid process is well
developed and is often forked. The clavicles are also well developed,
and vestiges of the precoracoid and of the sternal end of the coracoid
are often found.
In PRIMATES the clavicle and coracoid process are always well
developed. In Man and the Gorilla the scapula has a long straight
suprascapular border, a well-developed coracoid process and spine, and
a large curved acromion. Vestiges of the precoracoid occur at each end
of the clavicle. The shape of the scapula varies much in the lower
Primates.
THE UPPER ARM AND FORE-ARM.
In the MONOTREMATA the humerus is short, very broad at each end and
contracted in the middle. The radius and ulna are stout and of nearly
equal size, while the ulna has a greatly expanded olecranon.
In the MARSUPIALIA the humerus is generally a strong bone, broad at
the distal end and having well marked deltoid and supinator ridges,
which are specially large in _Notoryctes_. An ent-epicondylar or
supracondylar foramen (fig. 105, 5) is almost always present except in
_Notoryctes_. The radius and ulna are always distinct and well
developed, and a certain amount of rotation can take place between
them. The ulna of _Notoryctes_ has an enormous hooked olecranon which
causes the bone to be nearly twice as long as the radius.
[Illustration FIG. 105. ANTERIOR SURFACE OF THE RIGHT HUMERUS OF A
WOMBAT (_Phascolomys latifrons_). (After OWEN.)
1. head.
2. greater tuberosity.
3. lesser tuberosity.
4. deltoid ridge.
5. ent-epicondylar (supracondylar) foramen.
6. supinator ridge.
7. external condyle.
8. internal condyle.
9. articular surface for radius.
10. articular surface for ulna.]
EDENTATA. The Sloths have long slender arm bones; the humerus is
nearly smooth and has a very large ent-epicondylar foramen in
_Choloepus_, but not in _Bradypus_. The radius and ulna can be
rotated on one another to a considerable extent. The humerus in all
other Edentates is very strong and has the points for the attachment
of muscles much developed, especially in the Armadillos and
Megatheriidae. An ent-epicondylar foramen is found in all living
forms. The radius and ulna are well developed, but are not capable of
much rotation.
In the SIRENIA the humerus is well developed and of a normal
character. It is expanded at each end and has a prominent internal
condyle, a small olecranon fossa, and no ent-epicondylar foramen. In
the Dugong and _Rhytina_ there is a bicipital groove and the
tuberosities are distinct, but in the Manatee there is no bicipital
groove, and the tuberosities coalesce. The radius and ulna are about
equally developed and ankylosed together at both ends.
In the CETACEA the arm bones are very short and thick. The humerus has
a globular head, and a distal end terminated by two equal flattened
surfaces to which the radius and ulna are united. There is no
bicipital groove, and the tuberosities coalesce. The radius and ulna
are flat expanded bones fixed parallel to one another, but the ulna
has a definite olecranon. Scarcely any movement can take place between
them and the humerus, and in old animals the three bones are often
ankylosed together.
In the UNGULATA VERA the humerus is stout and rather short. The great
tuberosity is always large and often overhangs the bicipital groove,
it is especially large in _Titanotherium_ (_Brontops_). There is never
an ent-epicondylar foramen. The radius is always large at both ends,
but the condition of the ulna is very variable. Sometimes, as in
_Tapirus_, _Rhinoceros_, _Macrauchenia_, Suina and Tragulina, the ulna
is well developed, and quite distinct from the radius; but in most
forms, although complete, it is much reduced distally, and is fused to
the radius. Sometimes, as in the Horse and Giraffe, it is reduced to
the olecranon and to a very slender descending process which does not
nearly reach the carpus. In the Tylopoda, though the ulna is complete
and its distal end is often distinct, it has coalesced with the radius
throughout its whole length; the olecranon is generally very large.
SUBUNGULATA. In the large Condylarthra the humerus has an
ent-epicondylar foramen, and the radius and ulna are stout bones
nearly equal in size.
In _Procavia_ the humerus is rather long, and has a very prominent
greater tuberosity, and a large supra-trochlear fossa, but no
ent-epicondylar foramen.
In the Proboscidea the humerus is marked by a greatly developed
supinator ridge, and is very long, longer than the radius and ulna.
The ulna has a remarkable development, having its distal end larger
than that of the radius, it has also a larger articular surface for
the humerus than has the radius.
In RODENTIA the humerus varies much in its development according to
the animal's mode of life. In the Hares it is long and straight, with
a small distal end, and a slight deltoid ridge. In the Beaver on the
other hand the deltoid and supinator ridges are considerably
developed. There is generally a large supra-trochlear fossa, but no
ent-epicondylar foramen.
CARNIVORA. In the Carnivora vera the humerus has large tuberosities, a
prominent deltoid ridge and a deep olecranon fossa. The shaft is
generally curved, and an ent-epicondylar foramen is often found,
though not in the Canidae, Hyaenidae, and Ursidae. The radius and ulna
are never united. The radius (fig. 77, B) has a very similar
development throughout its whole length, while the ulna has a large
olecranon (fig. 77, C, 11) and a shaft tapering somewhat towards the
distal end.
In the Pinnipedia the arm bones are very strongly developed. The
humerus has a very prominent deltoid ridge, and the proximal end of
the ulna and distal end of the radius are much expanded.
In the INSECTIVORA the arm bones are well developed, and the radius
and ulna, though sometimes united, are generally distinct; as a rule
there is an ent-epicondylar foramen, but this is absent in the
Hedgehog. The Mole has an extraordinary humerus, very short and
curved, and much flattened and expanded at both ends. It articulates
both with the scapula and coraco-clavicle. The ulna has a greatly
developed olecranon.
In the CHIROPTERA both humerus and radius are exceedingly long and
slender; the ulna is reduced to little more than the proximal end and
is fused to the radius. There is no ent-epicondylar foramen.
All PRIMATES have the power of pronation and supination of the
fore-arm, by the rotation of the distal end of the radius round that
of the ulna.
In Man and the Anthropoid Apes the humerus is long and straight, and
has a globular head; neither of the tuberosities, nor the deltoid nor
supinator ridges are much developed. The olecranon fossa is deep and
there is no ent-epicondylar foramen. The radius is curved and has a
narrow proximal, and expanded distal end, the ulna is straighter than
the radius and has the distal end much smaller than the proximal; the
olecranon is not much developed.
In the lower Primates, although the radius and ulna are always quite
separate, the power of pronation and supination is not nearly so great
as in the higher forms. In most of the Cebidae and Lemurs an
ent-epicondylar foramen occurs.
THE MANUS.
The Manus is divisible into two parts, viz. the carpus or wrist, and
the hand which is composed of the metacarpals and phalanges. The
carpal bones are always modified from their primitive arrangement,
sometimes more, sometimes less. One modification however is always
found in mammals, viz. the union of carpalia, 4 and 5 to form the
_unciform_ bone. Two sesamoid bones are commonly developed, one on
each side of the carpus, the _pisiform_ or one on the ulnar side being
much the larger and more constant: it has been suggested that these
represent respectively vestiges of a prepollex and a post-minimus
digit[172].
One or more of the five digits commonly present may be lost, and
sometimes all are lost except the third. The terminal or ungual
phalanges of the digits are commonly specially modified to support
nails, claws, or hoofs. There are as a rule two small sesamoid bones
developed on the ventral or flexor side of the metacarpo-phalangeal
articulations, and sometimes similar bones occur on the dorsal or
extensor side.
MONOTREMATA. In _Echidna_ the carpus is broad, the scaphoid and lunar
are united and there is no centrale. The pisiform is large and several
other sesamoid bones occur. Each of the five digits is terminated by a
large ungual phalanx. In _Ornithorhynchus_ the manus is more slender,
but the general arrangement is the same as in _Echidna_.
MARSUPIALIA. The carpus has no centrale and the lunar is generally
small or absent. Five digits are almost always present. In _Choeropus_
however the only two functional digits are the second and third, which
have very long closely apposed metacarpals; the fourth digit is
vestigial, but has the normal number of phalanges, while the first and
fifth are absent. The manus in _Notoryctes_ is extraordinarily
modified, the scaphoid and all the distal carpalia are apparently
fused, the first, second, and fifth digits are very small, the third
and fourth, though having only one phalanx apiece, bear each an
enormous claw. Lying on and obscuring the ventral surface of the manus
is a large bone, probably a sesamoid.
Among the EDENTATA there is a great diversity in the structure of the
manus, the centrale is however always wanting, and except in _Manis_
the scaphoid and lunar are distinct. In the Sloths the manus is very
long, narrow, and curved, and terminated by two or three long hooked
claws, borne by the second and third, or the second, third and fourth
digits. The fifth digit is absent, and the fourth is represented only
by a small metacarpal. In the Anteaters the third digit is greatly
developed and bears a long hooked claw. In _Myrmecophaga_ all five
digits are fairly well though irregularly developed, in _Cycloturus_
the first, fourth, and fifth, are vestigial. In the Armadillos the
manus is broad, and has strongly developed ungual phalanges. The
digits, though almost always five in number, vary much in their
relative arrangement. In _Dasypus_ they are regular, but are
remarkably irregular in Priodon. The pollex is absent in Glyptodonts
and in _Megatherium._ In _Megatherium_ the fifth digit is clawless
while the second, third, and fourth bear enormous claws. In the
Manidae the scaphoid and lunar are united; five digits are present,
the third and fourth being very large, and all being terminated by
deeply cleft ungual phalanges. In _Orycteropus_ the pollex is absent,
while the other digits are terminated by pointed ungual phalanges.
In SIRENIA the general structure of the manus is quite of the ordinary
mammalian type. In _Manatus_ most of the bones of the carpus are
distinct, but in _Halicore_ many, especially those of the distal row,
have coalesced. The digits are always five in number and have the
normal number of flattened phalanges.
In the CETACEA, on the other hand, the manus is much modified by the
fact that the number of phalanges may be greatly increased above the
normal number of three, thirteen or fourteen sometimes occurring in
each digit. These are believed to be duplicated epiphyses. In the
Mystacoceti the manus remains largely cartilaginous, in the Odontoceti
it is better ossified, and the phalanges commonly have epiphyses at
both ends. In _Physeter_ the carpal bones also have epiphyses. The
carpus generally consists of six bones arranged in two rows of three
each. Five digits are generally present, but sometimes as in
_Balaenoptera musculus_, there are four, the third being suppressed.
Their relative development varies much. The Sperm Whale which till
recently was placed in the entrance hall of the Natural History Museum
at South Kensington has one phalanx to the first digit, four to the
second, five to the third, four to the fourth, and three to the fifth.
Generally the manus is short and broad, but sometimes, as in
_Globicephalus_, it is much elongated owing to the great development
of the second and third digits.
UNGULATA[173]. The manus of the members of this great order is of very
great classificatory and morphological importance. All the members
agree in having the scaphoid and lunar distinct, and in almost every
case the ends of the digits are either encased in hoofs or provided
with broad flat nails. It is by means of characters derived from the
manus and pes that the group is subdivided into the Ungulata vera and
the Subungulata.
In the UNGULATA VERA the manus is never plantigrade, and there are not
more than four digits, the pollex being almost always completely
suppressed: in _Cotylops_ among extinct Artiodactyla however a
vestigial pollex is found. The centrale is absent, and the magnum
articulates freely with the scaphoid, and is separated from the
cuneiform by the unciform and lunar. All the bones of the carpus
interlock strongly, and the axis of the third digit passes through the
magnum and between the scaphoid and lunar.
There is a very strong distinction between the manus of the suborders
Artiodactyla and Perissodactyla. In the Artiodactyla the axis of the
manus passes between the third and fourth digits, which are almost
equally developed and, except in the Hippopotami and some extinct
forms such as _Anoplotherium_, have their ungual phalanges flattened
on their contiguous surfaces.
In all _ARTIODACTYLA_ the third and fourth digits are large, but a
gradual reduction in the second and fifth can be well traced. Thus in
the Suina the second and fifth digits, though smaller than the third
and fourth, are well developed and all four metacarpals are distinct.
In the Tragulina too all four metacarpals are developed, and in
_Dorcatherium_ the third and fourth commonly remain distinct as in the
Suina. In the other Artiodactyla however the third and fourth
metacarpals are almost always united, though indications of their
separate origin remain. In some Ruminantia, such as many Deer, the
second and fifth digits are reduced to minute splint bones attached to
the proximal end of the fused third and fourth metacarpals, and to
small hoof-bearing phalanges, sometimes attached to splint-like distal
vestiges of the metacarpals, sometimes altogether unconnected with any
other skeletal structures. In some other Ruminants, such as the Sheep
and Oxen, the only remnants of the second and fifth digits are nodules
of bone supporting the hoofs, and in others, such as the Giraffe,
_Anoplotherium commune_, some Antelopes and the Tylopoda, all traces
of these digits have disappeared. The Camels differ from all living
Ungulata vera in not having the distal phalanges completely encased in
hoofs, and from all except the Hippopotami in placing a considerable
amount of the manus on the ground in walking.
[Illustration FIG. 106. MANUS OF PERISSODACTYLES.
_A._ LEFT MANUS OF _Tapirus_. (After VON ZITTEL.)
_B._ RIGHT MANUS OF _Titanotherium_. (After MARSH.)
_C._ LEFT MANUS OF _Chalicotherium gigantium_. (After GERVAIS.)
1. scaphoid.
2. lunar.
3. cuneiform.
4. trapezoid.
5. magnum.
6. unciform.
7. trapezium.
II, III, IV, V. second, third, fourth and fifth digits.]
While the manus of the Artiodactyla is symmetrical about a line drawn
between the third and fourth digits, that of the _PERISSODACTYLA_ is
symmetrical about a line drawn through the middle of the third digit,
which is larger than the others and has its ungual phalanx evenly
rounded and symmetrical in itself. The most reduced manus in the whole
of the mammalia is found in the Horse and its allies, in which the
third digit, terminated by a very wide ungual phalanx, is the only one
functional. Small splint bones representing the second and fourth
metacarpals are attached to the upper part of the third metacarpal. In
_Hipparion_[174] and other early horse-like animals the second and
fourth digits, though very small and functionless, are complete and
are terminated by small hoofs. In _Rhinoceros_ the second and fourth
digits are equally developed and nearly as large as the third, and
reach the ground in walking, a vestige of the fifth is also present.
In the Tapir (fig. 106, A) and _Hyracotherium_ the fifth digit is
fully developed but is scarcely functional. In _Titanotherium_
(_Brontops_) (fig. 106, B) it is nearly as well developed as any of
the others, and there is little or no difference between the relative
development of the third and fourth digits.
The Chalicotheriidae[175], though distinctly Perissodactyles in
various respects such as their cervical vertebrae and teeth, differ
not only from all other Perissodactyles, but from almost all other
Ungulates, in the very abnormal character of their manus. For while
the carpus and metacarpus are like those of ordinary Perissodactyles,
the phalanges resemble those of Edentates, each second phalanx having
a strongly developed trochlea, and each distal one being curved,
pointed and deeply cleft at its termination (fig. 106, C).
The Macraucheniidae, while agreeing with Perissodactyles in having
only three digits, with the limb symmetrical about a line drawn
through the middle of the third, have a carpus which approaches
closely to the subungulate condition, the magnum articulating
regularly with the lunar, and only to a slight extent with the
scaphoid.
In the SUBUNGULATA the manus sometimes has five functional digits, and
a considerable part of it rests on the ground in walking. The bones of
the carpus retain their primitive relation to one another, the magnum
articulating with the lunar, but not with the scaphoid. This character
does not however hold in the Toxodontia, for in most of the animals
belonging to this group the magnum does articulate with the scaphoid.
The corner of the scaphoid just reaches the magnum also in Amblypoda.
As far as is known the _TOXODONTIA_ generally have three, sometimes
five digits to the manus, and the third is symmetrical in itself--a
Perissodactyloid feature.
In _Phenacodus_ (fig. 107, B) (_CONDYLARTHRA_) all five digits are
well developed, the pollex being the smallest. The carpal bones retain
their primitive arrangement, the magnum articulating with the lunar
and not with the scaphoid. There is no separate centrale.
[Illustration FIG. 107. LEFT MANUS OF
_A. Coryphodon hamatus._ (After MARSH.) × 1/5.
_B. Phenacodus primaevus._ (After COPE.) × 1/3.
_C. Procavia (Dendrohyrax) arboreus._ (After VON ZITTEL.) × 6/7.
1. scaphoid.
2. lunar.
3. cuneiform.
4. trapezium.
5. trapezoid.
6. magnum.
7. unciform.
8. centrale.
9. pisiform.
I, II, III, IV, V. first, second, third, fourth and fifth digits
respectively.]
In the _HYRACOIDEA_ (fig. 107, C) the manus is very similar to that in
_Phenacodus_, but a centrale is present and the pollex is much
reduced.
The manus of the _AMBLYPODA_, such as _Coryphodon_ (fig. 107, A) and
_Uintatherium_, is short and broad, with five well developed digits
and large carpal bones. The carpals however interlock to a slight
extent, and the corner of the magnum reaches the scaphoid.
In the _PROBOSCIDEA_ the manus is very short and broad, with large
somewhat cubical carpals which articulate by very flat surfaces and do
not interlock at all. All five digits are present, and none of them
are much reduced in size. The manus in Proboscidea and in _Coryphodon_
is subplantigrade.
In the Tillodontia the manus is plantigrade and has pointed ungual
phalanges, in this respect approaching the Carnivora. It differs
however from that of all living Carnivora in having the scaphoid and
lunar distinct.
In RODENTIA the manus nearly always has five digits with the normal
number of phalanges: the pollex may however be very small as in the
Rabbit, or absent as sometimes in the Capybara. The scaphoid and lunar
are generally united, and a centrale may be present or absent. In
_Pedetes caffer_ the radial sesamoid is double and the distal bone
bears a nail-like horny covering. In _Bathyergus_ the pisiform is
double. It is upon these facts that the contention for the former
existence of prehallux and post-minimus digits has partly been based.
In living CARNIVORA the scaphoid, lunar and centrale are always
united, forming a single bone. All five digits are present, but as a
rule in Carnivora vera the pollex is small, and in _Hyaena_ is
represented only by a small metacarpal. Sometimes, as in Cats and
Dogs, the manus is digitigrade, sometimes, as in Bears, plantigrade.
The ungual phalanges are large and pointed, and in forms like the
Cats, whose claws are retractile, they can be folded back into a deep
hollow on the ulnar side of the middle phalanx; a small radial
sesamoid is often present.
In Pinnipedia the manus is large and flat and the digits are
terminated by ungual phalanges which are blunt (sea lions and walrus),
or slightly curved and pointed (seals). The pollex is nearly or quite
as long as the second digit, and as a rule the digits then
successively diminish in size.
The Creodonta differ from living Carnivora in the fact that the
scaphoid and lunar are usually separate.
In INSECTIVORA the scaphoid and lunar are sometimes united, sometimes
separate, and a separate centrale is usually present. There are
generally five digits, but sometimes the pollex is absent. In the Mole
the manus is greatly developed and considerably modified. It is very
wide, its breadth being increased by the great development of the
radial sesamoid which is very large and sickle-shaped. The ungual
phalanges are also large and are cleft at their extremities.
In the CHIROPTERA the manus is greatly modified for the purpose of
flight. The pollex is short and is armed with a rather large curved
claw, the other digits are enormously elongated, the elongation in the
case of the Insectivorous bats being mainly due to the metacarpals,
and in the Frugivorous bats to the phalanges. In the Frugivorous bats
the second digit is clawed as well as the pollex, in other bats this
claw is always absent, and so is often the ungual phalanx, the middle
phalanx then tapering gradually to its termination.
In PRIMATES as a rule the manus is moderately short and wide. The
carpus has the scaphoid and lunar distinct, and generally also the
centrale; sometimes however, as in Man, the Gorilla, Chimpanzee, and
some Lemurs, the centrale has apparently fused with the scaphoid.
There are almost always five well-developed digits, but in the genera
_Colobus_ and _Ateles_ the pollex is vestigial.
The magnum in man is the largest bone of the carpus. The pisiform also
is well developed, but there is no radial sesamoid. In Man, the
Gorilla, Chimpanzee, and Orang, the carpus articulates only with the
radius, in most Primates it articulates also with the ulna. The third
digit of the Aye-Aye (_Chiromys_) is remarkable for its extreme
slenderness.
THE PELVIC GIRDLE.
The pelvic girdle in all mammals except the Sirenia and Cetacea
consists of two halves, usually united with one another at the
symphysis in the mid-ventral line, and connected near their upper
ends, with the sacral vertebrae. Each half forms one of the
_innominate_ bones, and includes at least three separate elements, a
dorsal bone, the ilium, and two ventral bones, the ischium and pubis.
Very often a fourth pelvic element, the acetabular or cotyloid bone,
occurs.
In the MONOTREMATA the pelvis is short and broad, and the pubes and
ischia meet in a long symphysis. The acetabulum is perforated in
_Echidna_ as in birds, but not in _Ornithorhynchus_. A pair of
elongated slender bones project forwards from the edge of the pubes
near the symphysis; these are sesamoid bones formed by ossifications
in the tendons of the external oblique abdominal muscles, and are
generally called _marsupial bones_.
In the MARSUPIALIA the ilia are generally very simple, straight, and
narrow, while the pubes and ischia are well developed and meet in a
long symphysis. Marsupial bones are nearly always prominent, but are
not developed in _Thylacinus_ or _Notoryctes_. The ischium often has a
well-marked tuberosity and in Kangaroos the pubis bears a prominent
pectineal process on its anterior border close to the acetabulum. The
pelvis in _Notoryctes_ differs much from that in all other Marsupials,
the ilium and ischium being ankylosed with six vertebrae in a manner
comparable to that of many Edentates.
In the EDENTATA the pelvis is generally well developed, but the
symphysis is very short. In the Sloths the pelvis is rather weak and
slender, the obturator foramina are very large and the ischia do not
meet in a symphysis. In the Megatheriidae the pelvis is exceedingly
wide and massive, and is firmly ankylosed with a number of vertebrae.
In the Armadillos, Glyptodonts, Anteaters, and Pangolins it is much
developed and firmly united to the vertebral column by both the ilia
and the ischia. In _Orycteropus_ however the ischium does not become
united to the vertebral column, and the pubis generally has a strongly
developed pectineal process.
In the SIRENIA the pelvis is quite vestigial. In the Dugong it
consists on each side of two slender bones, one of which represents
the ilium and the other the ischium and pubis; the two bones are
placed end to end and are commonly fused together. The ilium is
attached by ligament to the transverse process of one of the
vertebrae. In the Manatee each half of the pelvis is represented by a
triangular bone connected by ligaments with its fellow and with the
vertebral column. In neither Manatee nor Dugong is there any trace of
an acetabulum but one can be made out in _Halitherium_.
In the CETACEA the pelvis is even more vestigial than in the Sirenia,
consisting simply of a pair of small straight bones which probably
represent the ischia, and lie parallel to and below the vertebral
column at the point where the development of chevron bones commences.
In UNGULATA VERA the pelvis is generally rather long and narrow. The
ilium is flattened and expanded in front (fig. 103, 8), but becomes
much narrower and more cylindrical before reaching the acetabulum.
Both pubis and ischium contribute to the symphysis which is often very
long. The ischia are large and have prominent tuberosities, especially
in Artiodactyles. In most Ruminantia there is a deep depression, the
supra-acetabular fossa above the acetabulum, but this is not found in
the Suina or Tylopoda.
SUBUNGULATA. In _Procavia_ the pelvis is long and narrow, and bears
resemblance to that in Artiodactyles.
The Proboscidea have a very large pelvis set nearly at right angles to
the vertebral column; the ilium is very wide, having expanded iliac[1]
and gluteal[1] surfaces, and a narrow sacral[176] surface. The pubes
and ischia are rather small, but both meet their fellows in the
symphysis. _Uintatherium_ (suborder Amblypoda) also has a large and
vertically placed pelvis (fig. 108) with a much expanded ilium. The
pelvis however differs from that of the Proboscidea in the fact that
the ischia do not meet in a ventral symphysis.
In many RODENTIA the ilia have their gluteal, iliac, and sacral
surfaces of nearly equal extent; in the Hares, however, the gluteal
and iliac surfaces are confluent. The pubes and ischia are always well
developed and sometimes, as in the Hares, the acetabular bone also. In
these animals the pubis does not take part in the formation of the
acetabulum, and the ischium bears on its outer side a well-marked
ischial tuberosity.
In the CARNIVORA the pelvis is long and narrow. The iliac surfaces
(fig. 78, A, 5) are very small and the sacral large; the crest or
supra-iliac border is formed by the union of the sacral and gluteal
surfaces. The symphysis is long and includes part of both pubis and
ischium. The ischial tuberosity (fig. 78, A, 10) is often well marked,
and sometimes as in _Viverra_ the acetabular bone is distinct. In the
Pinnipedia the pelvic symphysis is little developed, or sometimes not
developed at all, and the obturator foramina are remarkably large.
In some INSECTIVORA such as _Galeopithecus_, there is a long pelvic
symphysis, in others such as _Erinaceus_ and _Centetes_, it is very
short, in others again such as _Talpa_ and _Sorex_, there is no pelvic
symphysis. The acetabular bone is exceptionally large in _Talpa_ and
_Sorex_.
In CHIROPTERA the pelvis is small and narrow, and in the great
majority of cases the two halves do not meet in a ventral symphysis.
The pubis has a strongly developed pectineal process, which
occasionally unites with a process from the ilium enclosing a large
pre-acetabular foramen.
PRIMATES. In Man and the Anthropoid Apes the pelvis is very large and
wide, and the ilium has much expanded iliac and gluteal surfaces. The
symphysis is rather short and formed by the pubis alone. The
acetabulum is deep and the obturator foramen large, and there is
frequently a well-marked ischial tuberosity. In the lower Anthropoidea
the ilium is long and narrow and has a small iliac surface. The
ischial tuberosities are large in the old world monkeys.
[Illustration FIG. 108. LEFT ANTERIOR AND POSTERIOR LIMB AND LIMB
GIRDLE OF _Uintatherium mirabile_. The anterior limb is to the left,
the posterior to the right × 1/10. (From casts, Brit. Mus.)
1. ilium.
2. head of femur.
3. great trochanter.
4. patella.
5. fibula.
6. tibia.
7. second digit of pes.
8. ungual phalanx of fifth digit of pes.
9. calcaneum.
10. postscapular fossa.
11. prescapular fossa.
12. coracoid process.
13. humerus.
14. radius.
15. ulna.
17. unciform.
18. cuneiform.
20. lunar.
21. first metacarpal.
22. fifth metacarpal.]
THE THIGH AND SHIN.
In the MONOTREMATA the femur is short, rather narrow in the middle,
and expanded at each end. The great and lesser trochanters are large
and about equally developed, but there is no third trochanter. The
fibula is very large and is expanded at its proximal end, forming a
flattened plate much resembling an olecranon. The patella is well
developed.
In the MARSUPIALIA there is no third trochanter to the femur, the
fibula is well developed but not the patella as a general rule.
_Notoryctes_ has a femur with a prominent ridge extending some little
way down the shaft from the great trochanter; the tibia has a
remarkably developed crest, and the fibula has its proximal end much
expanded and perforated; there is an irregularly shaped patella
closely connected with the proximal end of the tibia.
EDENTATA. In the Sloths the leg bones are all long and slender. The
femur has no third trochanter, and the fibula is complete and nearly
equal in size to the tibia. In the Megatheriidae the leg bones are
extraordinarily massive, the circumference of the shaft of the femur
in _Megatherium_ equalling or exceeding the length of the bone. There
is no third trochanter in _Megatherium_. In most of the remaining
Edentata the leg bones are strongly developed. The femur in the
Armadillos and Aard Varks has a strong third trochanter, and the
tibia and fibula are both large and are commonly ankylosed together at
either end. The limb bones are very massive also in the Glyptodonts.
SIRENIA. In no living Sirenian is there any trace of a hind limb, but
in _Halitherium_ a vestigial femur is found, which articulates with
the pelvis by a definite acetabulum.
[Illustration FIG. 109. LEFT FEMUR OF AN OX (_Bos taurus_) (to the
left) AND OF A SUMATRAN RHINOCEROS (_R. sumatrensis_) (to the right).
× 1/6. (Camb. Mus.)
1. head.
2. great trochanter.
3. lesser trochanter.
4. third trochanter.
5. shaft.
6. condyles.]
In the Mystacoceti among the CETACEA small nodules of bone or
cartilage occur connected with the vestigial pelvis, and may represent
the femur and tibia. No trace of the skeleton of the hind limb is
known in the Odontoceti.
In the UNGULATA VERA the femur is noticeable for the size of the great
trochanter (fig. 109, 2); there is no definitely constricted neck
separating the head from the rest of the bone, and the lesser
trochanter (fig. 109, 3) is not very prominent. All Perissodactyles
except the Chalicotheriidae show a strongly marked third trochanter,
but this is absent in all known Artiodactyles. The development of the
fibula in general corresponds to that of the ulna. In _Rhinoceros_,
_Macrauchenia_, _Tapirus_ and the Suina it is distinct and fairly well
developed; in the Tragulina on the other hand it is vestigial, being
reduced to the proximal end only. In the Ruminantia and Tylopoda also,
it is much reduced forming merely a small bone attached to the distal
end of the tibia, sometimes, as in the Red deer a slender vestige of
the proximal end also is preserved quite detached from the distal
portion; in the Horse this proximal portion is all that there is found
of the fibula. The progressive diminution of the fibula can be well
seen in the series of forms that are regarded as the ancestors of the
Horse. The patella of the Ungulata vera is well ossified, but
fabellae[177] are not usually found.
SUBUNGULATA. Of the Toxodontia, _Toxodon_ has no third trochanter
while _Typotherium_ and _Astrapotherium_ have one. In the Condylarthra
the femur has well-marked lesser and third trochanters, and the fibula
and patella are well developed. In the Hyracoidea there is a slight
ridge on the femur in the place of the third trochanter, the fibula is
complete, but is generally fused to the tibia at its proximal end.
Of the Amblypoda, _Coryphodon_ has a third trochanter, but
_Uintatherium_ has none; in this respect, in the vertical position and
general appearance (fig. 108) of the limb, and in the articulation of
the fibula with the calcaneum, the leg of _Uintatherium_ closely
approaches that of the Proboscidea.
In the Proboscidea the femur is very long and straight, the
development of trochanters is slight, and the fibula though slender is
complete and articulates with the calcaneum.
A third trochanter is found in the Tillodontia.
In RODENTIA the femur is variable, the great trochanter is generally
large and so sometimes is the third as in the Hares. In most Rodents
as in the Beaver the fibula is distinct, sometimes as in the Hares it
is united distally with the tibia. The patella is well developed, and
so too are the fabellae as a general rule.
CARNIVORA. In the Carnivora vera the femur (fig. 79, A) is generally
rather straight and slender, and has a very distinct head. The fibula
(fig. 79, C) is always distinct and there is generally a considerable
interval between it and the tibia. Fabellae (fig. 79, 7) are commonly
present.
In the Pinnipedia the femur is short, broad and flattened, having a
prominent great trochanter. The fibula is nearly as large as the
tibia, and the two bones are generally ankylosed together at their
proximal ends.
The Creodonta differ from all living Carnivores in having a femur with
a third trochanter.
In the INSECTIVORA a third trochanter is sometimes developed. The
fibula is sometimes distinct, sometimes fused distally with the tibia,
thus differing from that of a Carnivore.
In CHIROPTERA the femur is straight, slender and rather short, with a
small but well-developed head. The fibula may be well developed or
quite vestigial or absent. Owing to the connection of the hind limb
with the wing membrane the knee joint is directed backwards.
In PRIMATES the femur is rather long and slender, having a nearly
spherical head and large great trochanter. The tibia and fibula are
always distinct and well developed. Fabellae are not found in the
highest forms but are generally present in the others.
THE PES.
The skeleton of the pes is in most respects a counterpart of that of
the manus. Just as in the manus if one digit is absent it is the
pollex, so in the pes it is the hallux. But while in the manus the
third digit is always well developed, however much the limb may be
modified, in the pes any of the digits may be lost. In all mammals the
tibiale and intermedium fuse to form the _astragalus_, and the fourth
and fifth tarsalia to form the _cuboid_. Sesamoid bones are
considerably developed. In almost every case the phalanges and first
metatarsal have epiphyses only on their proximal ends, while the
remaining four metatarsals have epiphyses only on their distal ends.
In the MONOTREMATA all the usual tarsal bones are distinct, and the
five digits have the normal number of phalanges. Several sesamoid
bones are developed, the most important one, found only in the male,
being articulated to the tibia and bearing the curious horny spur. The
ungual phalanges of the pes like those of the manus, are deeply cleft
at their extremities. In the Echidnidae the pes is turned outwards and
backwards in walking.
In the MARSUPIALIA the pes is subject to great modifications, but in
every case the seven usual tarsal bones are distinct. In the
Didelphyidae the foot is broad, all five digits are well developed,
and the hallux is opposable to the others. In the Dasyuridae the foot
is narrow, and the hallux may be very small, or as in _Thylacinus_
completely absent. In _Notoryctes_ the pes is much less abnormal than
the manus, and all five digits have the usual number of phalanges. The
fifth metatarsal has a curious projecting process, and there is a
large sesamoid above the hallux. In the Wombats (Phascolomyidae) the
foot is short and broad, the digits are all distinct, and the hallux
is divaricated from the others.
In the remaining marsupials the second and third metacarpals and
digits are very slender, and are enclosed within a common integument.
This condition is known as _syndactylism_, and its effect is to
produce the appearance of one toe with two claws. In the Kangaroos
(Macropodidae) the pes is very long and narrow, owing to the
elongation of the metacarpals. The fourth digit is greatly developed,
the fifth moderately so, while the hallux is absent, and the second
and third digits are very small. The Peramelidae have the foot
constructed on the same plan as in the Kangaroos, and in one genus
_Choeropus_ the same type of foot is carried to a greater extreme than
even in the Kangaroos. Thus the fourth digit is enormously developed,
the second and third are small, and the fifth smaller still, while the
hallux is absent. In the Phalangers and Koalas though the second and
third toes are very slender, the hallux is well developed and
opposable.
EDENTATA. In the Sloths the pes much resembles the manus, being long
and narrow, but in both genera the second, third and fourth digits are
well developed. Most of the other Edentates have a but little modified
pes with the normal number of tarsal bones and the complete series of
digits. In _Cycloturus_ however the hallux is vestigial and it is
absent in Glyptodonts. _Megatherium_ has a greatly modified pes, the
hallux is absent, and the second digit vestigial, while the third is
very large, having an enormous ungual phalanx. The calcaneum too is
abnormally large.
No trace of the pes occurs in either SIRENIA or CETACEA.
In the UNGULATA the pes like the manus is subject to much variation
and is of great morphological importance.
In the UNGULATA VERA the pes is never plantigrade and never has more
than four digits, the hallux being absent. The cuboid always
articulates with the astragalus, and the tarsal bones strongly
interlock. As was the case also with the manus, the pes is formed on
two well-marked types characteristic respectively of the Artiodactyla
and Perissodactyla.
_ARTIODACTYLA._ Just as in the manus, the third and fourth digits are
well and subequally developed; their ungual phalanges have the
contiguous sides flat, and the axis of the limb passes between them,
and between the cuboid and navicular. The astragalus has both the
proximal and distal surfaces pulley-like, and articulates with the
navicular and cuboid by two facets of nearly equal size. The calcaneum
articulates with the lower end of the fibula if that bone is fully
developed.
In the Suina four toes are developed, and though in the Peccaries the
third and fourth metatarsals are united, they are all distinct in most
members of the group, as are all the tarsal bones. In the Hippopotami
the four digits are of approximately equal size, and the middle ones
do not have the contiguous faces of their ungual phalanges flattened.
In the Tragulina the cuboid, navicular, and two outer cuneiforms are
united forming a single bone; all four metatarsals are complete and
the two middle ones are united. In the Tylopoda and _Anoplotherium
commune_ only the third and fourth digits are developed, their
metatarsals are free distally, but are elsewhere united. In the
Ruminantia the cuboid and navicular are always united and so are the
second and third cuneiforms, while in _Cervulus_ all four bones are
united together. The third and fourth metatarsals in Ruminants are
always united in the same way as are the third and fourth metacarpals,
while the second and fifth are always wanting. In Deer the second and
fifth digits are usually each represented by three small phalanges,
but in the Giraffe and most Bovidae the bones of these digits are
wanting.
[Illustration
FIG. 110. _A._ LEFT PES OF A TAPIR (_Tapirus americanus_). × 1/6.
_B._ RIGHT PES OF A RHINOCEROS (_R. sumatrensis_). × 1/8.
_C._ (CAST OF) RIGHT PES OF _Hipparion gracile_. × 1/7.
_D._ RIGHT PES OF A HORSE (_Equus caballus_). × 1/10. (All Camb. Mus.)
1. calcaneum.
2. astragalus.
3. navicular.
4. cuboid.
5. external cuneiform.
6. middle cuneiform.
7. internal cuneiform.]
In the _PERISSODACTYLA_ the pes like the manus is symmetrical about a
line drawn through the third digit; this line when continued passes
through the external cuneiform, navicular and astragalus. The
astragalus has its distal portion abruptly truncated, and the facet by
which it articulates with the cuboid is much smaller than that by
which it articulates with the navicular. The calcaneum does not
articulate with the fibula. The tarsus in _Macrauchenia_ like the
carpus differs from that of other Perissodactyles and resembles that
of Subungulates in having the bones arranged in lines with little or
no interlocking. The calcaneum resembles that of Artiodactyles in
having a small facet for articulation with the fibula. _Tapirus_ (fig.
110, A), _Rhinoceros_ (fig. 110, B) and _Titanotherium_ have a short
and broad foot with the usual tarsal bones and three well-developed
digits,--a number never exceeded by any Perissodactyle. From this
tridactylate limb a series of stages is exhibited by various extinct
forms leading gradually to the condition met with in the Horse (fig.
110, D) in which the third toe is greatly developed, while the second
and fourth are reduced to slender metatarsals attached to the proximal
half of the third metatarsal.
In _Chalicotherium_ and _Agriochoerus_ the pes has the same abnormal
characters as the manus, the digits being clawed and the ungual
phalanges in _Chalicotherium_ deeply cleft.
In the SUBUNGULATA the pes is sometimes plantigrade and
pentedactylate, the cuboid sometimes does not articulate with the
astragalus, and the tarsal bones sometimes do not interlock.
In _Typotherium_ (_TOXODONTIA_) the hallux is absent and the other
four digits are well developed; in _Toxodon_ and _Nesodon_ the pes is
tridactylate. The tarsal bones have the regular Subungulate
arrangement, the cuboid not articulating with the astragalus. The
calcaneum articulates with the fibula as in Artiodactyles. The
astragalus in most forms, but not in _Astrapotherium_, resembles that
of the Ungulata vera in having a grooved proximal surface.
In _Phenacodus_ (_CONDYLARTHRA_) the tarsus is very little modified,
five digits are present, the first and fifth being small and not
reaching the ground.
In _Procavia_ only the three middle digits are present with a vestige
of the fifth metacarpal.
In the _AMBLYPODA_ the pes (fig. 108) is very short and broad, all
five digits are functional, and at any rate in _Coryphodon_
plantigrade, the hallux being the smallest. The astragalus is very
flat, and the tarsals interlock to a slight extent, the cuboid
articulating with both calcaneum and astragalus.
The pes in the _PROBOSCIDEA_ much resembles that in the Amblypoda, but
differs in that the astragalus does not articulate with the cuboid,
the tarsals not interlocking at all.
In the RODENTIA the structure of the foot is very variable. In Beavers
the foot is very large, all five digits being well developed; the
fifth metatarsal articulates with the outer side of the fourth
metatarsal, and not with the cuboid, and there is a large sesamoid
bone on the tibial side of the tarsus. In the Rats, Porcupines and
Squirrels, there are five digits, in the Hares only four, and in the
Capybara and some of its allies only three. In the Jerboa (_Dipus_) a
curious condition of the pes is met with, as it consists of three very
long metatarsals fused together and bearing three short toes, each
formed of three phalanges. _Lophiomys_ differs from all other Rodents
in having the hallux opposable.
CARNIVORA. In the Carnivora vera the pes is regular and shows little
deviation from the normal condition. All the usual tarsal bones are
present, but sometimes as in the Dogs, Cats, and Hyaenas, the hallux
is vestigial. Sometimes as in the Bears the pes is plantigrade,
sometimes as in the Cats and Dogs it is digitigrade. In this respect
and in the character of the ungual phalanges, the pes closely
corresponds with the manus. In the Sea Otter (_Latax_) the foot is
large and flattened and approaches in character that of the
Pinnipedia.
In the Pinnipedia the pes differs much from that in the Carnivora
vera. In the Seals in which the foot cannot be used for walking, and
is habitually directed backwards, the first and fifth digits are much
longer and stouter than any of the others. In the Sea Lions which can
use the pes for walking, the digits are all of nearly the same length,
and in the Walrus the fifth is somewhat the longest.
In the INSECTIVORA the pes is almost always normal, and provided with
five digits.
In the CHIROPTERA the pes is pentedactylate, and the digits are
terminated by long curved ungual phalanges. In some genera the toes
have only two phalanges. The calcaneum is sometimes produced into a
long slender process which helps to support the membrane between the
leg and the tail.
Among the PRIMATES Man has the simplest form of pes. In Man all five
digits are well developed, the hallux being considerably the largest.
Sesamoid bones occur only under the metatarso-phalangeal joint of the
hallux.
In the other Primates the internal cuneiform has a saddle-shaped
articulating surface for the hallux, which is obliquely directed to
the side of the foot and opposable to the other digits. Two sesamoid
bones are usually developed below each metatarso-phalangeal joint, and
one below the cuboid. The second digit in Lemurs, and all except the
hallux in _Chiromys_ have pointed ungual phalanges; in all other cases
the ungual phalanges are flat. In some of the Lemuroidea, especially
_Tarsius_, the tarsus is curiously modified by the elongation of the
calcaneum and navicular.
FOOTNOTES:
[165] The figure was drawn from a photograph and the size of the jaws
relatively to the cranium is exaggerated.
[166] See W.K. Parker, "On the Structure and Development of the Skull
in the Pig." _Phil. Trans._ pp. 289-336, 1874.
[167] See W.H. Flower, "On the value of the characters of the base of
the cranium in the classification of the order Carnivora." _P.Z.S._
1869, p. 5.
[168] See W.K. Parker, _Monograph of the shoulder-girdle and sternum
of the Vertebrata_, _Ray Soc._ 1868.
[169] See p. 405.
[170] See E. Lydekker, _P.Z.S._ 1895, p. 172.
[171] See H. Wincza, _Morph. Jahr._ XVI. p. 647, 1890.
[172] See K. Bardeleben, _P.Z.S._, 1889, p. 259.
[173] See E. Cope, "The origin of the foot structures of Ungulata,"
_Journ. of Philad. Acad._ 1874. H.F. Osborn, "The evolution of the
Ungulate foot," _T. Amer. Phil. Soc._ 1889.
[174] See O.C. Marsh, various papers including "Fossil horses in
America," _Amer. Natural._ 1874; "Polydactyl horses," _Amer. J. Sci._
1879 and 1892. M. Pavlow, "Le développement des Equidés," _Bul. Soc.
Moscou_, 1887, and subsequent papers in the same. Osborn and Wortman,
"On the Perissodactyls of the White River beds," _Bull. Amer. Mus._
Dec. 23rd, 1895.
[175] See H.F. Osborn, _Chalicotherium and Macrotherium, Amer.
Natural._ 1889--91--92.
[176] See p. 409.
[177] See p. 412.
LIST OF AUTHORS REFERRED TO.
Abbott, E.C., 112
Ameghino, F., 351, 424
Andrews, C.W., 299
Balfour, F.M., 16
Ballowitz, E., 424
Bardeleben, K., 504
Bateson, W., 50, 344
Baum, H., 374
Baur, G., 27, 189, 190, 344, 346
Beneden, P.J. van, 353
Benham, W.B., 51
Bettany, G.T., 16, 87, 154
Boulenger, G.A., 169
Brandt, J.F., 352
Bridge, T.W., 123
Brühl, C.B., 210
Burmeister, H., 351, 424
Cope, E.D., 135, 199, 204, 351, 359, 361, 363, 368
Credner, H., 135
Dean, B., 63, 104
Dobson, G.E., 369, 370
Earle, C., 432
Ecker, A., 151
Ellenberger, W., 374
Flower, W.H., 28, 42, 351, 420, 422, 434
Fritsch, A., 135
Fürbringer, M., 295
Gadow, H., 40, 112, 190, 295, 343, 350
Gegenbaur, C., 127
Gervais, P., 353
Günther, A.C.L.G., 70, 104
Haslam, G., 151
Hasse, C., 112, 113
Haswell, W.A., 127
Hertwig, O., 169
Hoffmann, C.K., 190, 202, 210
Howes, G.B., 164, 451
Hubrecht, A.A.W., 104
Hulke, J.W., 192, 204
Hurst, C.H., 71, 297
Hutton, F.W., 299
Huxley, T.H., 11, 13, 133, 135, 191, 210, 295, 297, 334, 343, 351,
374, 437
Kirkaldy, J.W., 51
Klein, E., 11
Kölliker, A., 9
Kükenthal, W., 349, 422
Lankester, E. Ray, 51
Leche, W., 344, 423
Lindsay, B., 336
Lydekker, R., 36, 42, 190, 195, 495
Macbride, E.W., 50
Marsh, O.C., 204, 209, 299, 348, 361, 364, 365, 508
Marshall, A.M., 71, 151
Masterman, A.T., 51
Meyer, H. v., 135
Miall, L.C., 135, 243
Mivart, St G., 369
Morgan, C. Lloyd, 11
Newton, E.T., 283
Osborn, H.F., 348, 420, 429, 508
Owen, R., 191, 204, 210, 297, 348, 351, 420
Parker, T.J., 83, 96, 299
Parker, W.K., 16, 24, 53, 87, 154, 173, 200, 243, 465, 489
Pavlow, M., 358, 508
Pollard, H.B., 119
Poulton, E.B., 422
Pycraft, W.P., 297
Ridewood, W.G., 106, 164
Röse, C., 422
Sagemehl, M., 104
Schäfer, E., 11
Scott, W.B., 368
Seeley, H.G., 191, 212
Selenka, E., 40, 295
Shufeldt, R., 123
Smith, E. Noble, 11
Stirling, E.C., 423
Swirski, G., 103
Taeker, J., 427
Thomas, O., 349, 362, 370, 422, 424, 425
Tomes, C.S., 420
Traquair, R.H., 55, 58
Vogt, C., 297
Wiedersheim, R., 25, 134, 136
Wincza, H., 358, 495
Woodward, A. Smith, 34, 54, 58, 62, 127, 210
Wortman, J.L., 508
Wray, R.S., 303
Zittel, K.A. v., 36, 205, 212
INDEX.
Every reference is to the page: words in italics are names of
genera or species; figures in italics indicate that the
reference relates to systematic position; figures in thick type
refer to an illustration; _f._ = and in following page or
pages; _n._ = note.
Aard Vark, _44_, _352_;
femur, 517;
sacrum, 452;
teeth, 425;
see _Orycteropus_
Aard wolf, _48_;
see _Proteles_
Abdominal ribs, crocodile, 260;
reptiles, 286
Abdominal shield, turtle, 215
_Acanthias_, _32_;
calcification of vertebrae, 114;
pectoral fins, 130
_Acanthodes_, _32_, _64_
Acanthodii, _32_;
general characters, 64;
spines, 106
_Acanthomys_, _47_;
spines, 417
Acanthopterygii, _34_
Accipitres, _41_
Acetabular bone, 25, 513;
dog, 409 f.;
frog, 165
Acetabulum, 25;
crocodile, 266;
dog, 409;
duck, 324;
frog, 165;
newt, 149;
turtle, 235
_Acipenser_, _32_, 117;
exoskeleton, 67;
distribution, 66;
pectoral fins, 131;
plates, 104;
skull, 121, =122=;
spinal column, 112
Acipenseridae, _32_
Acrodont, defined, 199;
teeth of reptiles, 273
_Acrodus_, _32_;
teeth, 109
Acromion, dog, 405
_Actinotrocha_, _30_;
organ regarded as double notochord, 51
Ad-digital quill, duck, 303
Adjutant, _41_;
clavicles, 338
Ægithognathous, 335
Æluroidea, _48_, _369_;
teeth, 437
Æpyornis, _40_;
tibio-tarsus, 341
Æpyornithes, _40_, _299_
Aftershaft, 328
_Agama_, _38_;
teeth, 273
Agamidae, _38_;
premaxillae, 284
Aglossa, _36_
Agouti, _48_;
see _Dasyprocta_
Agriochoeridae, _45_
_Agriochoerus_, _45_;
pes, 525
Ala spuria, duck, 304
Alcidae, _42_;
see Auks
Alisphenoid, 19;
crocodile, 247;
duck, 317;
dog, 386
_Alligator_, _39_, _210_, _212_;
hyoid, =285=;
limbs, =264=;
pectoral girdle, =262=;
pelvis and sacrum, =267=;
scutes, 271;
skull, =245=, =248=, =253=
Alligatoridae, 39
_Alytes_, _36_;
fronto-parietal fontanelle, 179;
vertebrae, 172
Amblypoda, _47_;
general characters, 363;
manus, 510;
pes, 525;
skull, 473;
teeth, 433;
thigh and shin, 519
_Amblystoma_, _35_;
skull, 175
American monkeys, _373_;
see _Cebidae_
American vultures, _41_;
vomers, 335
_Amia_, _33_;
distribution, 66;
exoskeleton, 67;
pectoral fin, 131;
scales, 105;
skull, 123;
tail, 115, 117;
vertebrae, 114
Amiidae, _33_
_Ammocoetes_, _31_, _55_
Amphibia, _35_;
anterior limb, 185;
exoskeleton, 168;
general characters, 133;
hyoid apparatus, 180;
pectoral girdle, 184;
pelvic girdle, 187;
posterior limb, 188;
ribs, 182;
skull, 173;
sternum, 182;
teeth, 169;
vertebral column, 170
Amphicoelous, defined, 14
_Amphioxus_, _30_;
skeleton, 51 f.;
spinal column, 112
_Amphisbaena_, _38_, 272;
loss of limbs, 289
Amphisbaenidae, _38_, _200_;
pectoral girdle, 288;
skull, 277;
vertebral column, 275
Amphitheriidae, _43_
_Amphiuma_, _35_, _135_;
manus, 187;
pes, 188;
skull, 174
Amphiumidae, _35_
Anacanthini, _33_
Anal shield, turtle, 215
_Anas_, _41_;
_A. boschas_, see Duck
Ankylosis, defined, 12
Angel fish, _32_
Angler, attachment of teeth, 107
Anguidae, _38_
_Anguilla_, _33_;
see Eel
_Anguis_, _38_;
loss of limbs, 289;
scutes, 271
Angular, 22;
cod, 100;
crocodile, 258;
duck, 319;
salmon, 94;
turtle, 231
Angulo-splenial, frog, 161
Ankle joint, duck, 327;
reptiles, 294
Anomodontia, _36_
Anoplotheriidae, _45_
_Anoplotherium_, _45_;
manus, 506;
pes, 523;
tail, 454;
teeth, 428
_Anser_, _41_
Anseres, _41_;
aftershaft, 329;
claws, 330
Anseriformes, _41_
Anteaters, _352_;
absence of teeth, 424;
manus, 505;
pectoral girdle, 495;
pelvis, 513;
skull, 458;
thoraco-lumbar vertebrae, 447;
Spiny --, _43_;
Great and Two-toed --, _44_
Antelope, _359_;
manus, 507;
Four-horned A., _46_
Anterior limb, 26;
Amphibia, 185;
birds, 338;
crocodile, 263;
dog, 405;
duck, 322;
frog, 164;
newt, 147;
reptiles, 290;
turtle, 232
Anthropoid apes, _373_;
arm-bones, 503;
pelvis, 515
Anthropoidea, 49;
general characters, 372;
sacrum, 452;
skull, 482;
teeth, 441
_Anthropopithecus_, _49_;
ribs, 493
Antiarcha, _31_;
general characters, 55
Antibrachium, see fore-arm
_Antilocapra_, _46_;
horns, 417
Antilocapridae, _46_
Antitrochanter, duck, 325
Antlers, 8, 358;
Cervidae, 469
Antorbital process, 18
Anura, _36_;
general characters, 136;
hyoid apparatus, 180;
pelvis, 187;
posterior limb, 188;
skull, 179;
sternum, 182;
vertebrae, 172
_Apatornis_, _40_;
vertebrae, 332
Apteria, 328
Apteryges, _40_
_Apteryx_, _40_, _299_;
aftershaft, 329;
anterior nares, 333;
claws, 330;
foot, 342;
manus, 338;
pectineal process, 341;
pectoral girdle, 338;
pneumaticity of skeleton, 331;
_A. oweni_, pelvic girdle and sacrum, =340=
Aqueductus vestibuli, dogfish, 74
Arcade:
infratemporal--, crocodile, 255;
_Sphenodon_, 283;
inner --, duck, 318;
outer --, duck, 318;
supratemporal --, crocodile, 257;
reptiles, 281
Archaeoceti, _44_;
general characters, 356;
skull, 461;
teeth, 426
_Archaeopteryx_, _40_, _297_;
claws, 330;
fibula, 341;
mandible, 335;
metatarsals, 342;
pelvis, 341;
ribs, 336;
sacrum, 333;
skull, 333;
tail, 333;
teeth, 330;
wing, 338
Archaeornithes, _40_;
characters, 297
_Archegosaurus_, _35_, _136_;
palatines, 177
Archipterygium, _Ceratodus_, 127;
Ichthyotomi, 62
Arcifera, _36_, 185
Arctoidea, _48_, 369;
teeth, 438
_Ardea_, _41_;
see Heron
Ardeae, _41_
Arm, see fore-arm and upper arm
Armadillo, _44_, _352_;
cervical vertebrae, 443;
femur, 517;
humerus, 501;
lumbar vertebrae, 447;
manus, 505;
pectoral girdle, 495;
pelvis, 513;
ribs, 491;
sacrum, 452;
scales, 417;
scutes, 419;
skull, 459;
teeth, 424
Armour plates, 8
Arthrodira, _34_;
characters, 70
Articular, 22;
cod, 100;
crocodile, 258;
duck, 319;
newt, 144;
salmon, 94;
turtle, 231
Artiodactyla, _45_;
characters, 358;
manus, 506;
odontoid process, 445;
pes, 522;
ribs, 491;
skull, 465;
teeth, 427;
thoraco-lumbar vertebrae, 448
Asses, _360_
_Asterolepis_, _31_, _55_
Asterospondyli, 114
Astragalus, 27;
crocodile, 268;
dog, 414;
mammals, 521
Astrapotheriidae, _46_
_Astrapotherium_, _46_, 361;
dental formula, 432;
femur, 519;
pes, 525
_Ateles_, _49_;
pollex, 512;
tail, 454
Atlantosauridae, _38_
Atlas, 15;
crocodile, 240;
dog, =379=, 380;
duck, 309;
ox, =445=;
turtle, 219
Attachment of teeth, 4;
in fish, 107
_Auchenia_, _45_;
see Llama
Auditory aperture or meatus:
external --, crocodile, 250;
dog, 402;
turtle, 228;
internal --, crocodile, 246, 251;
dog, 392;
turtle, 228
Auditory capsule, 20;
cod, 96;
crocodile, 250;
dog, 390;
dogfish, 74;
frog, 156;
newt, 143;
turtle, 227
Auditory ossicles, crocodile, 251;
dog, 393;
duck, 320;
mammals, 485 f.;
turtle, 228
Auks, _42_;
thoracic vertebrae, 332
Autostylic, 61, 119
Aves, _40_;
characters, 295;
see Birds
Axial skeletal rods, 50
Axial skeleton, crocodile, 239;
cod, 83;
dog, 377;
dogfish, 72;
duck, 307;
frog, 152;
newt, 138;
turtle, 218
Axis vertebra, crocodile, 241;
dog, 380;
duck, 309;
turtle, 220
Axolotl, _35_;
see _Siredon_
Aye Aye, _49_;
see _Chiromys_
_Babirussa_, _45_;
dental formula, 428
Baboon, _49_;
see _Cynocephalus_
_Balanoglossus_, _30_, 50
_Balaena_, _44_, _357_;
scapula, 495;
_B. mysticetus_ baleen, 419
Balaenidae, _44_
Balaenoidea, _44_;
general characters, 356
_Balaenoptera_, _44_, 357;
manus, 506;
thoracic vertebrae, 448;
scapula, 495;
_B. musculus_, cervical vertebrae, =444=
Baleen, 3, 418
_Balistes_, _33_;
teeth, 111
Balistidae, _33_
Ball and socket joints, 13
Bandicoot, _43_
Barb, 302
Barbule, 303
Barramunda, _34_;
see _Ceratodus_
Basalia, dogfish, 79
Basibranchial, dogfish, 78;
cod, 101;
duck, 320;
newt, 145;
salmon, 95
Basi-branchiostegal, cod, 101;
salmon, 95
Basicranial axis, 19;
dog, 384
Basidorsalia, dogfish, 72
Basi-hyal, dogfish, 78;
dog, 399;
duck, 320
Basilar plate, 17
Basilingual plate, Anura, 180;
crocodile, 259;
frog, 161;
turtle, 231
Basi-occipital, 19;
crocodile, 246;
cod, 97;
dog, 386;
duck, 315;
salmon, 89;
turtle, 224
Basipterygium, cod, 103;
dogfish, 82
Basisphenoid, 19;
crocodile, 247;
dog, 386;
salmon, 91;
turtle, 225
Bastard wing, duck, 304
Bathyerginae, palate, 366
_Bathyergus_, _47_;
auditory ossicles, 488;
manus, 511
Batoidei, _32_, 64
_Batrachoseps_, _35_;
teeth, 169
Bats, claws, 418;
Horseshoe bats, _49_;
see Chiroptera
_Bdellostoma_, _31_, _55_;
teeth, 57
Beak, 3;
birds, 329;
duck, 302;
_Siren_, 168;
tadpoles of Anura, 168;
turtle, 215
Bears, _48_, _369_;
manus, 511;
pes, 526;
sacral vertebrae, 452;
skull, 479;
Isabelline -- mandible, =438=
Beaver, _47_;
fibula, 520;
humerus, 502;
pes, 526;
sacrum, 452;
tail, 454
_Belodon_, _39_, 211;
frontals, 277;
palate, 281;
vertebrae, 275
Bichir, _33_;
see _Polypterus_
Bicipital groove, dog, 405
Bilophodont, defined, 345;
teeth of Tapiridae, 429
_Bipes_, _38_;
limbs, 289
Birds, anterior limb, 338;
endoskeleton, 331 f.;
exoskeleton, 328 f.;
general characters, 295;
hyoid, 336;
pectoral girdle, 336;
pelvic girdle, 339;
posterior limb, 341;
ribs, 336;
skull, 333;
sternum, 336;
teeth, 330;
vertebral, 332
_Bison_, _46_;
occipital crest, 468
Blind snake, _38_;
see _Typhlops_
Blind worm, _38_;
see _Anguis_
Boidae, _38_
_Bombinator_, _36_;
vertebrae, 172
Bone, development of, 10 f.
Bone cells, 10
Bony Ganoids, fins, 105;
pelvic fin, 132;
ribs, 126;
skull, 123;
vertebral column, 114;
see _Holostei_
Border:
alveolar --, of dog's jaw, 398;
coracoid, glenoid, and suprascapular -- of dog's scapula, 405
_Bos_, _46_;
occipital crest, 468;
ribs, 491;
see Ox
Bottlenose, _44_;
see _Hyperoödon_
Bovidae, _46_;
pes, 523;
skull, 468
Bow-fin, _33_;
see _Amia_
Brachial ossicles, cod, 103
Brachium; see upper arm
Brachydont, defined, 345;
teeth of Ungulates, 429 f.
_Brachycephalus_, _36_;
bony plates of, 168
Brain case, crocodile, 245;
dog, 384;
duck, 314;
frog, 154;
newt, 140;
turtle, 224
Bradypodidae, _43_;
see Sloths
_Bradypus_, _43_;
cervical vertebrae, 443;
pectoral girdle, 495;
skull, 457;
thoraco-lumbar vertebrae, 447
Branchial arches, Amphibia, 180 f.;
cod, 101;
dogfish, 78;
fish, 120 f.;
newt, 145;
salmon, 95;
-- basket, Marsipobranchii, 38;
-- skeleton, _Amphioxus_, 52;
Balanoglossus, 50
_Branchiosaurus_, _35_;
branchial arches, 180
Branchiostegal rays, cod, 100
_Brontops_, _46_;
see _Titanotherium_
_Brontosaurus_, _38_, _207_;
sternum, 288
_Bubalus_, _46_;
ribs, 491;
see Buffalo
Buccal skeleton, _Amphioxus_, 52
_Buceros_, _42_;
see Hornbill
Buckler, of Labyrinthodonts, 168, 184
Buffalo, _46_;
Cape --, skeleton of, =492=
_Bufo_, _36_;
hyoid, 182;
jaws, 169;
_B. viridis_, carpus, 186
Bufonidae, _36_
Bunodont, defined, 345;
teeth of Ungulata, 427 f.
Buno-selenodont, defined, 432
Caeciliidae, _35_
_Caiman_, _39_;
_C. latirostris_ hyoid, =285=,
limbs, =264=,
lateral view of skull, =248=,
palatal view of cranium and mandible, =245=,
longitudinal section of skull, =253=,
pectoral girdle, =262=,
pelvic girdle and sacrum, =267=;
_C. sclerops_, scutes, 271
Ca'ing whale, _45_;
see _Globicephalus_
_Calamoichthys_, _33_;
distribution, 66
Calamus, 302
Calcaneum, 27;
crocodile, 268;
dog, 414
Calcar, of frog, 167
_Callorhynchus_, _32_, _66_;
teeth, 110
Camel, _45_, _359_;
manus, 507;
teeth, 428
Camelidae, _45_
_Camelus_, _45_;
see Camel
Camptosauridae, _39_
Canal:
alisphenoid --, dog, 402;
carotid --, duck, 315;
Eustachian --, crocodile, 247;
dog, 402;
duck, 316;
interorbital --, dogfish, 76
Canaliculi, 10
Canidae, _48_;
humerus, 502;
skull, 479;
see Dog
Canine, 344;
dog, 376 f.
_Canis_, _48_;
thoraco-lumbar vertebrae, 450;
see Dog
_Capitosaurus_, _35_;
skull, =176=
Capybara, _48_;
manus, 511;
pes, 526;
skull, 476;
tail, 454
Carapace, Chelonia, 271;
_Dermochelys_, 272;
Glyptodonts, 419;
Green turtle, 215;
Loggerhead turtle, =216=
Carcharidae, _32_
Carina sterni, duck, 321
Carinatae, _40_;
general characters, 300;
quadrate, 334
Carnassial teeth, 368;
carnivora, =436=;
dog, 376 f.
Carnivora, _48_;
arm bones, 502;
auditory ossicles, 488;
cervical vertebrae, 446;
general characters, 367;
manus, 511;
pelvis, 515;
pes, 526;
ribs, 493;
sacral vertebrae, 452;
skull, 478;
sternum, 490;
tail, 454;
teeth, 437;
thigh and shin, 520;
thoraco-lumbar vertebrae, 450
Carnivora vera, _48_;
general characters, 368;
scapula, 497
Carp, _33_;
pharyngeal teeth, 111
Carpo-metacarpus, duck, 324
Carpus, 26;
crocodile, 265;
dog, 408;
duck, 323;
frog, 164;
newt, 147;
turtle, 233
Cartilage, structure of, 10
Cartilaginous ganoids, cranium, 121;
pelvic fin, 132;
spinal column, 112;
see Chondrostei
Cassowary, _40_, _299_;
aftershaft, 328;
bony crest, 334;
claws, 330;
pelvic girdle and sacrum, =340=;
secondaries, 329
_Castor_, _47_;
see Beaver
Castoridae, _47_
_Casuarius_, _40_;
see Cassowary
Cataphracti, _34_
Cat, _48_, _369_;
hallux, 526;
manus, 511;
skull, 479
Cat-fish, _33_
Cathartae, _41_
_Cathartes_, _41_;
see American vulture
Caudal fin, Cetacea, 453;
fish, 116;
-- vertebrae, crocodile, 243;
cod, 85;
dog, 383;
duck, 312;
general characters, 16;
newt, 140;
turtle, 222
_Cavia_, _48_;
tail, 454
Caviidae, _48_
Cebidae, _49_, _373_;
ribs, 493;
skull, 484;
teeth, 441
_Coenolestes_, _43_, 424
Cement, 5
_Centetes_, _49_;
caudal vertebrae, 454;
pelvic symphysis, 515;
spines, 417;
teeth, 440;
thoraco-lumbar vertebrae, 450
Centetidae, _49_;
auditory ossicles, 488;
skull, 480
Centrale, 27;
see Carpus and Tarsus
Centre of motion, 448
Centrum, 14
_Cephalaspis_, _31_, _55_
Cephalic shield, armadillos, 419
_Cephalochordata_, _30_, 51
_Cephalodiscus_, _30_, 50
_Ceratodus_, _34_, _70_;
branchial arches, 124;
cranium, =125=;
skeleton, =128=;
skull, 117, 124;
spinal column, 113;
teeth, 111
Cerato-branchial, cod, 101;
dogfish, 78;
duck, 320;
salmon, 95
Cerato-hyal, 23;
cod, 100;
dog, 399;
dogfish, 78;
salmon, 95
_Ceratophrys_, _36_;
bony plates of, 168;
teeth, 170
_Ceratops_, _39_;
see _Polyonax_
Ceratopsia, _39_;
characters, 209;
premaxillae, 284
Ceratopsidae, _39_
_Ceratosaurus_, _38_, 208;
supratemporal fossae, 283;
_C. nasicornis_, skeleton, =206=
Cercopithecidae, _49_, _373_
Cervical ribs, crocodile, 260;
reptiles, 285
Cervical vertebrae, crocodile, 239;
dog, 380;
duck, 307;
general characters, 15;
mammals, 442;
turtle, 219
Cervidae, _46_;
skull, 469
_Cervulus_, _46_;
pes, 523
_Cervus_, 46;
_C. megaceros_, antlers, 469
_Cestracion 32_;
calcification of vertebrae 114;
external branchial arches 121;
pectoral fin 130;
skull =118=;
suspensorium 119;
teeth 109;
vertebral column 114
Cestraciontidae _32_
Cetacea _44_, 522;
arm bones 501;
auditory ossicles 487;
caudal vertebrae 453;
cervical vertebrae 444;
characters 353;
exoskeleton 416 f.;
hind limb 518;
manus 505;
pectoral girdle 495;
pelvis 514;
position of limbs 28;
ribs 491;
skull 461 f.;
sternum 489;
teeth 426;
thoraco-lumbar vertebrae 448
Cetiosauridae _38_
_Chalcides_ _38_;
limbs 289
Chalicotheriidae _46_;
femur 519;
manus 509
_Chalicotherium_ _46_;
femur 360;
pes =508=, 525;
teeth 432
_Chamaeleon_ _38_, 199 f.;
epipubis 293;
ilia 291;
manus 291;
skull 278
Chamaeleonidae _38_
Charadriidae _42_
Charadriiformes _42_
_Chauna_ _41_;
interorbital septum 333;
ribs 336;
_C. derbiana_, spurs 330
_Chelone_ _37_, _194_;
plastron 271, =218=;
see Turtle
Chelonia _37_;
beaks 271;
carapace 271;
general characters 193;
humerus 290;
limbs 290;
palate 281;
pectoral girdle 288;
pelvic girdle 291;
skull 277 f.;
tarsus 293;
vertebrae 275 f.
Chelonidae _37_
Chelydae _37_
_Chelydra_ _37_;
carpus 26, 291
Chelydridae _37_
_Chelys_ _37_, _195_
Chersidae _37_
Chevron bones 16;
crocodile 243;
mammals 453 f.;
reptiles 276
Chevrotain _45_, _359_;
teeth 429
_Chimaera_ _32,_ _66_;
attachment of fins 130;
pelvic girdle 127;
skull =65=;
teeth 110
Chimaeridae _32_
Chimaeroidei, general characters 65
Chimpanzee _49_;
carpus 512;
ribs 493;
thoraco-lumbar vertebrae 450
_Chinchilla_ _47_;
auditory ossicles 488
Chinchillidae _47_
Chiromyidae _49_
_Chiromys_ _49,_ _372_;
manus 512;
pes 527;
teeth 441
Chiroptera _49_;
auditory ossicles 488;
arm bones 503;
cervical vertebrae 446;
general characters 370;
manus 512;
pelvis 515;
pes 527;
sacrum 452;
shoulder girdle 499;
skull 481;
sternum 490;
tail 454;
teeth 440;
thigh and shin 520;
thoraco-lumbar vertebrae 450
_Chirotes_ _38_;
limbs 289
_Chlamydophorus_ _44,_ _272_;
scutes 419;
skull 459
_Chlamydoselache_ _31_;
branchial arches 121
_Choeropus_ _43_;
manus 504;
pes 522
_Choloepus_ _43_;
ribs 491;
shifting of pelvis 451;
skull =458=;
sternum 489;
thoraco-lumbar vertebrae 447;
_C. hoffmanni_ cervical vertebrae 443
Chondrocranium, salmon 87
Chondroid tissue, _Balanoglossus_ 50
Chondrostei _32_;
fins 105;
general characters 67;
teeth 110;
see Cartilaginous ganoids
Chordal sheath, _Amphioxus_ 52
Chrysochloridae _49_
_Chrysochloris_ _49_;
auditory ossicles 488;
claws 418;
teeth 440
_Ciconia_ _41_;
see Stork
Ciconiiformes _41_
Cingulum 376
Civet _48,_ _369_;
teeth 437
_Cladoselache_ _31,_ _63_; fin 129
Clasper 132;
dogfish 82
Clavicle 25;
birds 338;
cod 102;
duck 322;
dog 405;
fish 126;
frog 163;
mammals 494 f.;
reptiles 289
Claws 3;
birds 330;
crocodile 237;
dog 374;
duck 302;
mammals 417;
turtle 215
Clupeidae, _33_
_Clupeus_, _33_
Cnemial crest, dog, 412;
duck, 326
_Coccosteus_, _34_, _70_
Coccyx, man, 454
Cochliodontidae, _31_
_Cochliodus_, _31_;
dental plates, 109
Cod, _33_;
appendicular skeleton, 101 f.;
cranium, 96;
mandibular and hyoid arches, =99=;
median fins, 86;
pectoral girdle and fin, =102=;
ribs, 86;
skull, 96 f.;
vertebral column, 83 f.
_Coelogenys_, _48_;
zygomatic arch, 477
_Coenolestes_, _43_, 424
Coffer-fish, _33_;
see, _Ostracion_
_Colobus_, _49_;
pollex, 512
Colubridae, _38_
Columbae, _42_
Columbidae, _42_
Columella, crocodile, 251;
duck, 320;
frog, 157;
turtle, 228
Columella cranii, 200 n;
see epipterygoid
Colymbi, _40_
Colymbiformes, _40_
Compsognathidae, _38_
_Compsognathus_, _38_, 208
Condylar ridge, duck, 326
Condyle of humerus, dog, 406;
of mandible, dog, 398
Condylarthra, _47_;
femur, 519;
general characters, 361;
manus, 509;
skull, 472;
teeth, 432
Contour feather, duck, 303
Copula, 23
_Coracias_, _42_;
see Roller
Coraciae, _42_
Coraciiformes, _42_
Coracoid, 25;
cod, 103;
crocodile, 263;
duck, 322;
frog, 163;
Monotremata, 493;
newt, 147;
reptiles, 288;
turtle, 232
Coracoid groove, duck, 321
Cormorant, _41_;
foot, 342;
skull, 335
Cornu, see hyoid
Cornua trabeculae, 18
_Coryphodon_, _47_;
femur, 519;
manus, 510;
pes, 525;
skull, 473;
teeth, 433;
_C. hamatus_, manus, =510=
Coryphodontidae, _47_
Costal plate, turtle, 215;
-- process, duck, 321;
-- shield, turtle, 214
Cotyloid bone, 25, 513;
see Acetabular bone
Cotylopidae, _45_
_Cotylops_, _45_;
pollex, 506;
skull, 468
Coverts, 306, 328
Cranium, 18;
cod, 96 f.;
crocodile, 244 f.;
development of, 16 f.;
dog, 384 f.;
dogfish, 73 f.;
duck, 314;
frog, 154 f.;
newt, 140 f.;
turtle, 222 f.
Cranio-facial axis, dog, 384
Creodonta, _48_;
carpus, 512;
femur, 520;
general characters, 368;
skull, 479;
teeth, 439
Cribriform plate, dog, 388, 400
Crocodile, _210_, _212_;
anterior limb, 263;
exoskeleton, 237;
pectoral girdle, 262;
pelvic girdle, 266;
posterior limb, 268;
ribs and sternum, 259;
skeleton, 237 f.;
skull, 243 f.;
tarsus, 293;
teeth, 238;
vacuities in surface of cranium, 256;
vertebral column, 239
Crocodilia, _39_;
general characters of, 210;
palate, 281;
skull, 277 f.;
succession of teeth, 274;
teeth, 273
Crocodilidae, _39_
_Crocodilus_, _39_;
_C. palustris_, sternum and associated bones, =261=;
late thoracic and first sacral vertebrae, =242=;
_C. vulgaris_, cervical vertebrae, =239=
Crossopterygii, _33_;
general characters, 68
Crotalidae, _38_
_Crotalus_, _38_;
jaws 280;
see Rattlesnake
Crows, _42_
Crura of stapes, dog, 393
Cruro-tarsal, ankle joint, 345
Crus, 26;
crocodile, 268;
dog, 412;
duck, 326;
frog, 166;
newt, 149;
turtle, 235
Crusta petrosa, 5
_Cryptobranchus_, _35_, 135;
skull, 175;
_C. lateralis_, sacral vertebrae, 171
Cryptodira, _37_;
characters, 194
Ctenoid scales, 8, 60, 105
Cubitals, 303 f.
Cuboid, 27;
dog, 415
Cuckoo, foot, 342
Cuculi, _42_
Cuculiformes, _42_
Cuneiform bones, 27;
dog, 414 f.
_Cyclodus_, _38_;
see _Tiliqua_
Cycloid scales, 8, 60, 105;
cod, 83
_Cyclopidius_, _45_;
skull, 468
Cyclospondyli, 114
Cyclostomata, _31_;
general characters, 53
_Cycloturus_, _44_;
hallux, 522;
manus, 505
_Cygnus_, _41_;
see Swan
_Cynocephalus_, _49_;
cervical vertebrae, 446;
skull, 482
Cynoidea, _48_, _369_;
dental formula, 437
_Cynognathus_, _36_;
occipital condyle, 277;
teeth, 273
Cyprinidae, _33_
_Cyprinus_, _33_;
see Carp
Cypseli, _42_
Cypselidae, _42_;
see Swifts
Cystignathidae, _36_
_Dactylopterus_, _34_;
pectoral fins, 131
Dasypodidae, _44_
_Dasyprocta_, _48_;
auditory ossicles, 488;
thoraco-lumbar vertebrae, 450
Dasyproctidae, _48_
_Dasypus_, _44_;
manus, 505;
skull, 459;
stapes, 487;
teeth, 424
Dasyuridae, _43_, _350_;
dentition, 423;
pes, 521;
skull, 456
Deer, _359_;
manus, 507;
pes, 523;
Chinese water --, _46_,
see _Hydropotes_;
Musk --, _46_,
see _Moschus_;
Red -- fibula, 519
Delphinidae, _45_
_Delphinus_, _45_, 357;
lumbar vertebrae, 448;
skull, 462 f.
Deltoid ridge, crocodile, 263;
dog, 406;
frog, 164
_Dendrohyrax_, 363
Dental formula, regular, 344, 422;
Anthropoidea, 441;
_Astrapotherium_, 432;
_Babirussa_, 428;
Camel, 428;
_Chiromys_, 441;
Chiroptera (many), 440;
Cynoidea, 437;
_Dinotherium_, 434;
Dog, 376;
Duplicidentata, 435;
_Elephas_, 434;
_Erinaceus_, 440;
_Felis_, 437;
_Galeopithecus_, 440;
_Hippopotamus_, 427;
Horse, 430;
_Hydromys_, 436;
Hyracoidea, 362;
Macropodidae, 423;
_Manatus_, 425;
_Notoryctes_, 423;
_Otaria_, 439;
_Procavia_, 432;
_Pteropus_, 441;
Rodentia (most), 435;
Ruminantia, 429;
_Squalodon_, 427;
_Sus_, 428;
Tapiridae, 429;
_Thylacinus_, 423;
_Uintatherium_, 433;
_Ursus_, 439;
_Zeuglodon_, 426
Dentary, 22;
crocodile, 258;
cod, 100;
duck, 320;
frog, 161;
newt, 144;
salmon, 94;
turtle, 230
Dentine, 5
Derbian Screamer, spurs, 330
Dermal exoskeleton, crocodile, 237;
fish, 105;
mammals, 419;
reptiles, 271;
turtle, 215
Dermo-supra-occipital, Labyrinthodontia, 177;
_Polypterus_, 122
Dermochelydidae, _37_
_Dermochelys_, _37_, _194_, 214, 270;
carapace and plastron, 272
Dermoptera, _48_;
general characters, 370
Derotremata, _35_
_Desmodus_, _49_;
teeth, 441
Desmognathous, 319, 335
Development of bone, 10;
of cranium, 16;
of teeth, 7
_Dicynodon_, _36_, _192_;
beak, 271;
supratemporal fossa, 283;
teeth, 273
Didelphia, _43_;
general characters, 349
Didelphyidae, _43_, _350_;
auditory ossicles, 486;
pes, 521;
teeth, 423
_Didelphys_, _43_;
atlas, 443;
teeth, 422
_Didus_, _42_;
see Dodo
Digitigrade, defined, 358 n.
Digits, _26_;
see Manus and Pes
_Dimetrodon_, _36_;
thoracic vertebrae, 276
_Dinichthys_, _34_, _70_
Dinocerata, 364;
see Uintatheriidae
Dinornithes, _40_, _299_;
see Moas
Dinosauria, _38_;
general characters, 204;
humerus, 290;
ischium, 291;
pectoral girdle, 288;
pes, 293;
pre-orbital vacuity, 284;
ribs, 285;
vertebrae, 275 f.
Dinotheriidae, _47_
_Dinotherium_, _47_, 365;
dental formula, 434;
teeth, 345
_Diodon_, _33_;
beaks, 111;
_D. hystrix_, scales, 105
Diphycercal tail, 60, 116
Diphyodont, defined, 7, 344
_Diplacanthus_, _32_, _64_
Dipneumona, _34_
Dipnoi, _34_;
general characters, 69;
pelvic fins, 131;
skull, 124;
spinal column, 113;
tail, 116;
teeth, 111
Dipodidae, _47_
Diprotodont, 423
Diprotodontia, _43_;
characters, 350
Dipteridae, _34_, _70_;
cranium, 124;
tail, 117;
teeth, 111
_Dipus_, _47_;
cervical vertebrae, 446;
pes, 526
Discoglossidae, _36_
_Discoglossus_, _36_;
ribs, 182;
vertebrae, 172
Distal, defined, 23 n.
Divers, _40_;
thoracic vertebrae, 332
_Docidophryne_, _36_;
shoulder girdle and sternum, =183=
Dodo, _42_;
wing, 338
Dog, _48_;
arm bones, =407=;
anterior limb, 405;
atlas and axis, =379=;
cranium, 384, =389=, =396=;
dentition, =375=;
innominate bone, =410=;
leg bones, =411=;
manus, 408, =413=, 511;
pectoral girdle, 404;
pelvic girdle, 409;
pes, =413=, 414;
posterior limb, 412;
ribs, 402;
second lumbar vertebra, =382=;
second thoracic vertebra, =382=;
skull, 383, =387=;
sternum, =403=, 404;
vertebral column, 378
Dogfish, _64_;
cranium, 73;
exoskeleton, 71;
median fins, 79;
pectoral girdle and fin, 79;
pelvic girdle, 81;
pelvic fin, 81;
ribs, 73;
skull, 73, =75=;
vertebral column, 72;
visceral skeleton, 77;
Spotted and Spiny --, _32_
Dolphin, _45_, _357_;
lumbar vertebrae, 448;
Gangetic --, _45_,
see _Platanista_
Donkey, skull, =431=
_Dorcatherium_, _45_;
manus, 507
Dorsal vertebra, 16
Dorsal shield, crocodile, 238
Down feathers, 306
_Draco_, _38_;
ribs, 286
Dromaeognathous, 335
_Dromaeus_, _40_, _299_;
see Emeu
Duck, _41_, 334;
beak, 329;
claws, 330;
cranium, =313=;
exoskeleton, 302;
pectoral girdle, 321;
pelvic girdle, 324, =311=, =325=;
pes, 327;
posterior limb, 326;
ribs, 320;
skull, 312, =312=, =313=;
sternum, 321;
vertebral column, 307;
wing, 322, =304=, =305=
Duckbill, _43_;
see _Ornithorhynchus_
Dugong, _44_;
humerus, 501;
pelvis, 514;
thoraco-lumbar vertebrae, 448;
see _Halicore_
Duplicidentata, _48_, 366;
dental formula, 435;
skull, 478
Eagles, 335
Eared Seals, _369_;
scapula, 498;
see Otariidae
_Echidna_, _43_;
caudal vertebrae, 453;
manus, 504;
pelvis, 513;
sacral vertebrae, 451;
shoulder-girdle and sternum, =494=;
skull, 455;
spines, 417;
spur, 418;
thoraco-lumbar vertebrae, 447
Echidnidae, _43_;
pes, 521
Ectethmoid, 21 n.
Ectocondylar ridge, dog, 406
Edentata, _43_;
auditory ossicles, 487;
arm bones, 500;
caudal vertebrae, 453;
cervical vertebrae, 443;
manus, 504;
pectoral girdle, 495;
pes, 522;
pelvis, 513;
ribs, 491;
sacrum, 452;
skull, 457;
sternum, 489;
teeth, 424;
thigh and shin, 517;
thoraco-lumbar vertebrae, 447
Eel, _33_;
scales, 105