the second. The segments of the three posterior pair are somewhat
protuberant, bearing six pair of short, strong spines, graduated in
length, between which there is a very thick, longitudinal brush of
short, fine, straight bristles, of which the lower ones are the longest;
some thick, minute spines arise from the upper lateral edges of the
segments. The spines in the dorsal tufts are short, much crowded, and of
nearly equal length; see figure, 27, Pl. X, in the allied _P.
polymerus_. In a specimen in which the sixth cirrus had seventeen
segments, the first cirrus had, in the shorter ramus, eight segments, of
which the lower four were thick and protuberant, with the spines doubly
serrated. In this same specimen, the anterior ramus of the second cirrus
had twelve segments, of which the five basal ones were highly
protuberant, and thickly clothed with non-serrated spines. In the third
cirrus the basal segments of the anterior ramus are highly protuberant.
The basal segments in the posterior rami of both these cirri, are
slightly protuberant, but otherwise resemble the segments in the three
posterior pair.
The _Caudal Appendages_ (Pl. X, fig. 22), in full-grown specimens, just
exceed in length the lower segments of the pedicels of the sixth cirrus;
they are nearly cylindrical, bluntly pointed, with five oblique
imperfect articulations; the lower or basal articulations cannot be
traced all round, being distinct only on the ventral surface. There is a
row of short spines round the upper edge of each segment, with a little,
short tuft on the point of the terminal segment. In a rather young
specimen, however, with its capitulum one fifth of an inch long, each
appendage certainly consisted of a single segment, with spines only on
the summit.
_Penis_ purple, with excessively short and fine spines in tufts, chiefly
near the extremity. In a specimen with a capitulum only one fifth of an
inch long, the penis consisted of a mere pointed papilla, not so long as
the caudal appendage, and therefore equalling in length only the lower
segment of the pedicel of the sixth cirrus.
_Ovigerous fræna._--I could see none, though there were two large
lamellæ in the sack. The ova were flesh-coloured, but they had been
dried and then placed in spirits. The ova were wonderfully numerous,
oval, much elongated, and 1/100th of an inch in length.
2. POLLICIPES ELEGANS.
POLLICIPES ELEGANS. _Lesson._ Voyage de la Coquille, tom. ii, p.
441, 1830, et Illust. Zool., Pl. xxxix, 1831.
---- RUBER. _G. B. Sowerby._ Zoolog. Proc., 1833, p. 74.
_P. capitulo, valvarum duobus aut pluribus sub-rostro verticillis
instructo: valvis et pedunculi squamis rufo-aurantiacis: squamarum
verticillis densis symmetricè dispositis._
Capitulum with two or more whorls of valves under the rostrum: valves
and scales of peduncle reddish-orange; the latter symmetrically arranged
in close whorls.
Maxillæ with three tufts of fine bristles, separated by larger spines;
segments is in the first cirrus more than half the number of those in
the sixth cirrus; caudal appendages multi-articulate; filamentary
appendages attached to the prosoma.
Coast of Peru, Payta, attached to wooden posts, according to
Lesson: Lobos Island, Peru, Mus. Cuming: West Coast of Mexico,
Tehuantepec, on an exposed rock, according to Hinds.
The resemblance of this species is so close to _P. cornucopia_, that it
is quite useless to do more than point out the few points of difference.
Valves of the capitulum and scales of the peduncle, coloured (after
having been in spirits,) reddish-orange. In a specimen in which the
capitulum was 1.3 of an inch in length, there were three whorls of
valves below the carina; in this large specimen altogether there were
about eighty valves; in medium-sized specimens, the number is about the
same as in _P. cornucopia_. The upper latus, (viewed internally,) has an
area about twice as large as that latus, which corresponds to the
interspace between the carina and terga; whereas in _P. cornucopia_ the
upper latus is only slightly larger than this same valve. The apex of
the basal internal margin of the carina is here rounded, instead of
being square, as is generally the case with _P. cornucopia_. The strong
membranous margin of the orifice of the sack, in its upper part, is
almost one third as wide as the widest part of the terga, whereas in _P.
cornucopia_ it is only one fourth of this same width. The peduncle
apparently is rather longer, compared with _P. cornucopia_, and the
calcareous scales on it perhaps a little larger in proportion.
In a very young specimen, with the capitulum barely exceeding 1/20th of
an inch in length, I could distinguish the sub-rostrum, sub-carina, the
upper, and some of the lower latera.
_Filamentary Appendages._--These, in a medium-sized specimen, are
arranged on the prosoma in four longitudinal approximate rows, there
being twelve in each row; those in the two outer rows are only half the
length of those in the two inner rows; those nearest the thorax are the
longest; there are some papillæ outside the outer rows. In a very large
specimen with its capitulum 1.3 in length, these filaments were very
much more numerous, and some were placed on the first segment of the
thorax, and at the bases of several of the posterior cirri. Some of the
filaments are bifid, trifid, and even branched. In all the specimens, at
the bases of the first pair of cirri, there are, on each side, a pair of
filaments, (one below the other,) pointing upwards, less than half as
long as those on the prosoma: also on each side of the mouth, there is a
longer and thicker filament, pointing upwards, with a few very minute
scattered spines on it; the apices of these three pair of filaments, as
well as of some of the others, are roughened with very minute pectinated
scales. All these filaments were gorged with the branching testes.
_Mouth._--The parts are closely similar to those in _P. cornucopia_; in
the mandibles, the interspace between the third tooth and the inferior
angle, is slightly pectinated: in the maxillæ, there are six or eight
pairs of spines between the two upper tufts of fine spines.
_Cirri._--These are in most respects similar, to those of _P.
cornucopia_. In a specimen in which the sixth cirrus had eighteen
segments, the shorter ramus of the first pair had ten segments, of which
the five lower segments were thick and clothed with doubly serrated
spines. In the second cirrus the anterior ramus had fifteen segments, of
which the four basal ones were highly protuberant, and thickly clothed
with spines. These spines, and some on the third cirrus, and a few on
the first cirrus, have peculiar bent teeth, presently to be described
under _P. polymerus_. These singularly toothed spines are absent in _P.
cornucopia_. From the above numbers, we see that the first and second
pairs of cirri have more segments in proportion to the sixth pair, than
in _P. cornucopia_; and in the second pair, a fewer proportional number
of the basal segments are protuberant and thickly clothed with spines.
_Caudal Appendages_, shorter than the lower segments of the pedicels of
the sixth cirrus, with only four articulations; rather constricted near
the base.
The _Ovigerous Fræna_ consist of very long and prominent folds, thinning
out to nothing towards the bases of the scuta, but not furnished, as far
as I could see, with glands, and therefore not normally functional.
_Diagnosis with P. cornucopia._--The reddish-orange colour of the valves
alone suffices. There is a very slight difference, in the larger
proportional size of the upper latera, and in the outline of the basal
margin of the carina. In the maxillæ there is, in _P. elegans_, a
greater width between the two upper tufts of fine spines. In the cirri,
the segments in the first pair, are more than half as many as those in
the sixth pair; in the anterior ramus of the second pair, only 4/15ths
of the segments are protuberant and brush-like, whereas in _P.
cornucopia_ 5/12ths are in this condition.
3. POLLICIPES POLYMERUS. Pl. VII, fig. 2.
POLLICIPES POLYMERUS.(!) _G.B. Sowerby._ Proc. Zool. Soc., 1833,
p. 74.
--MORTONI. (!) _Conrad._ Journal Acad. Nat. Sci. Philadelphia,
vol. vii, p. 261, Pl. xx, fig. 12, 1837.
_P. capitulo, valvarum duobus, tribus, aut pluribus sub-rostro
verticillis instructo: valvis sub-fuscis: lateribus à supremo ad infimum
gradatim quoad magnitudinem positis: carinæ margine basali (introrsùm
spectanti) ad medium excavato: pedunculi squamarum verticillis densis,
symmetricè dispositis._
Capitulum with two, three, or more whorls of valves under the rostrum:
valves brownish: latera regularly graduated in size from the uppermost
to the lowest: carina with the basal margin, (viewed internally,)
hollowed out in the middle: scales of the peduncle symmetrically
arranged in close whorls.
Maxillæ with three tufts of fine bristles, separated by larger spines;
caudal appendages uniarticulate; filamentary appendages attached to the
prosoma.
Upper California, St. Diego and Barbara, 32° to 35° N.,
according to Conrad; Mus. Cuming: Low Archipelago, Pacific
Ocean; Mus. Coll. of Surgeons: Southern Pacific Ocean, collected
during the Antarctic Expedition, Mus. Brit.
_Capitulum_, but little compressed, broad, with the scuta and terga
placed in a more oblique direction, with respect to the peduncle, than
is usual, so that the line of orifice forms an unusually small angle
with the basal margin of the capitulum. The capitulum is composed of
several whorls of valves, which gradually decrease in size from above
downwards. In a medium-sized specimen there were four whorls under the
rostrum; in the lowest of these whorls, there were between eighty and
ninety valves, and in the whole capitulum from one hundred and seventy,
to one hundred and eighty. The valves in the lower whorls are not of
equal sizes. Viewed externally, the valves seem to touch and overlap
each other; viewed internally (Pl. VII, fig. 2 _a_) they are found to be
just separated from each other by transparent membrane; none of the
valves are articulated together. The outer surfaces of nearly all the
valves, except in the two last formed whorls, are much disintegrated,
and seem to be composed of alternate white and brown layers of shell.
The membrane connecting the valves, as well as that of the peduncle, (in
specimens long kept in spirits,) is brown; but in some dried specimens,
there are indications of its having been coloured crimson (as in _P.
cornucopia_), round the orifice and between the valves.
_Scuta_, irregularly oval, convex, narrow at the upper end; basal margin
may be almost said to be formed of three short, unequal margins,
corresponding with the rostrum, the rostral and the adjoining latus. The
edge corresponding with the latter, is the best marked, and is generally
slightly hollowed out, as if a piece had been broken off. The
tergo-lateral margin is curved and protuberant. The umbo projects a
little over the scutal margin of the terga.
_Terga_, projecting beyond the other valves to an unusually small
degree, broadly oval; basal angle bluntly pointed, apex rounded, blunt;
scutal margin, hollowed out to receive the upper part of the tergal
margin of the scuta; carinal margin curved and protuberant; occludent
margin consists of two short sides at right angles to each other. The
whole valve in length and area is about equal to the scuta; internally,
somewhat concave.
_Carina_, triangular, rather narrow, internally deeply concave, very
slightly curled inwards; basal margin protuberant, with a large central
portion considerably hollowed out.
_Rostrum_, triangular, of nearly the same shape as the carina, but only
one third of its length, internally very slightly concave, and with the
basal margin various, being either truncated or angularly prominent in
the middle.
_Latera._--The upper pair (corresponding to the interval between the
scuta and terga) is only a trifle larger than the latera immediately
beneath; and these only a little larger than those lower down. In the
lowest whorl, the valves are very minute, though still about twice as
large as the scales on the peduncle, and of a different shape from them.
The upper latera (viewed internally) are almost diamond-shaped, owing to
the prominence of the basal margin, but this varies considerably in
degree. The latera in the next whorl are triangular, with the basal
margins protuberant and arched, in a less and less degree in the lower
whorls, until in the lowest, the valves are elongated transversely.
_Microscopical Structure._--A valve placed in acid leaves a thick opaque
mass, formed of three different kinds of tissue, one having a finely
shaded appearance; a second with a largely hexagonal reticulated
structure, and the third thin, transparent, and marked with arborescent
lines, which I imagine to be tubes, as will be hereafter seen in
Lithotrya. Near the exterior surface, there are many tubuli. It appears
to me probable that the strong tendency which the valves in this species
have to disintegrate, is connected with the unusual quantity of
animalized tissue contained by them. Externally the valves are covered
by a strong membrane, either white or yellow, or white streaked with
yellow, and marked by lines of growth, and by longitudinal, sinuous,
little ridges.
_Peduncle_, in the upper part, of rather less diameter than the
capitulum; twice or thrice as long as it; tapering a little downwards;
surface of attachment wide and flat. Calcareous scales, minute,
symmetrically and closely packed together: each scale is much flattened,
and its shape, including the imbedded portion, is that of a spear with
its point broken off. The basal end of each scale is conically hollow,
and from the layers of growth conforming to this hollow, there is a
false _appearance_ of an open tube running through the scale.
_Attachment._--The surface of attachment is wide: the two cement-ducts,
after running down the sides of the peduncle in a sinuous course, within
the longitudinal muscles and close outside the ovarian tubes, pass
through the corium, and then separately form the most abrupt loops or
folds. These are represented in Pl. IX, fig. 2, in which a space about
1/10th of an inch square is given, as seen from the outside. At each of
the bends, an aperture has been formed through the membrane of the
peduncle, and cement poured forth. The manner in which the discs of
cement (_b_) come out of the two ducts (_a_ _a_), and reach the external
surface, is shown in the section, figure 2 _a´_. The two tubes are
firmly attached to the older layers of membrane, and are covered by the
last-formed layers. In a young specimen, the cement-ducts were a little
above 2/2000ths of an inch in diameter, which had increased, in a
medium-sized specimen, to 5/2000. The cement-glands are retort-shaped,
seated near each other, high up in the peduncle.
_Size._--The largest specimen which I have seen, was three inches in
length including the peduncle; the capitulum was 9/10ths of an inch
long, and one in width.
_Young Specimen._--I examined one with a capitulum 18/1000ths of an inch
long, measured from the lowest whorl to the tips of the terga; the width
was only 13/1000ths of an inch; in old specimens the width of the
capitulum is greater than the length. The length of one of the scuta was
14/1000ths of an inch, therefore, greater than the width of the entire
capitulum, which is not the case with mature specimens. Besides the
scuta and terga, the carina and rostrum, and three pair of large latera,
there was a lower whorl formed of ten or twelve valves, giving
altogether to the capitulum of this very small specimen, either
twenty-two or twenty-four valves.
_Shape of Body, Sack, Colours, &c._--From the position of the orifice of
the capitulum, the animal’s body is suspended to the scuta in a more
transverse direction than is usual. The prosoma is well-developed, and
is distinctly separated from the three posterior thoracic segments, by
a band of thin membrane. The tunic of the basal part of the sack, where
it enters the peduncle in a blunt point, is thickened and covered with
roughened rounded papillæ. The corium of the sack under the valves, is
coloured (after spirits) so dark a brown as to be nearly black; the
cirri and trophi are similar, but with a tinge of greenish-purple.
_Filamentary Appendages._--Of these there were, on the prosoma of one
specimen, twelve pairs, and in another specimen fourteen pairs, seated
in two approximate rows; the middle filaments are the longest, equalling
about half the diameter of the thorax: each is flattened, and tapers but
little towards its summit, which is roughened with microscopical crests
serrated on both sides; on the summit, also, there are a few bristles
and some very short, thick, minute spines. These appendages are directed
rather towards each other, and towards the thorax. I do not doubt that
their numbers vary according to the size of the specimen. I believe that
they are occupied by testes. Outside these filaments, on each side of
the prosoma, there are two very irregular rows of papillæ, intermediate
in length between the filaments and the rounded swellings at the bottom
of the sack. Beneath the basal articulation of the first cirrus, there
is on each side, a short appendage, with a few bristles on its summit.
Lastly, on each side of the middle of the mouth, on the prosoma, there
is a longer appendage, dark-coloured, furnished with a few scattered
bristles on its sides and apex, and directed upwards and a little
towards the adductor scutorum muscle.
_Mouth._--Labrum highly bullate, but with the uppermost part not more
bullate than the lower part, and therefore not overhanging it; basal
margin much produced; crest with some small blunt teeth and some
bristles. The inner fold of the labrum is much thickened, yellow,
punctured, and with a tuft of fine bristles on each side.
_Palpi_, approaching each other but not touching, club-shaped, or with
broad and square extremities, thickly fringed with serrated bristles.
_Mandibles_ with three unusually strong teeth, slightly graduated in
size, with the inferior angle very coarsely pectinated; the lower edges
of the main teeth are roughened.
_Maxillæ_, (Pl. X. fig. 13). Spinose edge about half the length of the
mandibles; the two upper spines are unusually strong; close under, and
almost hidden by them, there is a tuft of fine spines; in the middle
there is a second similar tuft mounted on a prominence; and at the
inferior angle there is a third tuft, also mounted on a rather wider
prominence, not quite accurately figured. In the interspaces between
these tufts there are three or four pairs of spines of the usual
appearance and projecting just beyond the fine tufts; the upper of the
two interspaces is rather narrower, but rather deeper, than the lower
interspace. Apodeme very long, irregularly shaped, like an =S=, with a
remarkable elbow near its attachment; apex slightly enlarged, thin and
rounded.
_Outer Maxillæ._--On the inner margin there is a deep and conspicuous
notch, above and beneath which, there is a compact row of serrated
bristles; exteriorly the bristles are rather longer.
_Olfactory Orifices_ very prominent, pointing obliquely towards each
other.
_Cirri._--Posterior cirri moderately long, much curled, with the
segments (Pl. X, fig. 27) flattened and wide; the anterior surface
hemispherically protuberant, supporting six pairs of spines, of which
the lower ones approach each other; between these spines there is a
large tuft of very fine spines, of which the central ones are the
longest; there is an upper lateral group of very short strong spines;
dorsal tufts composed of short, fine numerous spines. _First pair_
seated close to the second pair, short, having in both rami eight
segments, whereas in the same individual the second pair, which is
nearly twice as long, had thirteen, and the sixth pair eighteen
segments. Rami of the first pair nearly equal in length, with their
segments, excepting the two upper ones, thickly paved with bristles, in
the midst of which a tuft of fine spines, as in the posterior cirri,
may be distinguished; the dorsal tufts encircle the whole of each
segment; the spine-bearing anterior surfaces are protuberant chiefly in
the upper part, so that they are oblique. The posterior (?) ramus has
its segments much wider than those on the other ramus; and amongst the
common spines, in the third and fourth segments, (counting from the
bottom,) there are some very strong spines with their upper ends
coarsely and doubly pectinated, each tooth being upwardly bent into a
rectangular elbow. In the fifth segment, some of the spines are doubly
pectinated with simple teeth; and most of the spines are doubly
serrated. The _Second_ (Pl. X, fig. 25) and _Third cirri_ have the five
basal segments (5/13ths of the whole number in the second cirrus, and
5/14ths in the third cirrus) of their anterior rami, extremely broad,
protuberant, and paved with serrated bristles, amongst which, (except on
the actual lowest segment,) there are some simply pectinated spines, and
others with their teeth elbowed, exactly as in the first cirrus. The
basal segments of the posterior rami of the second and third cirri,
differ from the three posterior cirri only in the spines being slightly
more numerous; but none of them are pectinated.
_Pedicels_, rather short; the upper segment resembles, in the
arrangement of its spines, the segments of the posterior cirri; the
lower segment is longer than the upper, and has _two_ tufts of fine
spines, between the two rows of long spines. In the second and third
cirri, these two intermediate tufts on the lower segment of the pedicel,
are not so distinctly separated from each other.
_Caudal Appendages_, very small, uniarticulate, blunt and rounded; tips
bearing a few, very short, thick spines.
_Alimentary Canal._--OEsophagus, somewhat curved at the lower end, where
it enters the stomach, which has no cæca; rectum, unusually short,
extending from the anus only to the base of the fifth pair of cirri.
Within the stomach, from top to bottom, there were thousands of a
bivalve entomostracous crustacean.
_Generative System._--Both ovaria and testes are largely developed; the
former fill the long peduncle; the testes enter both the pedicels of the
cirri, and the filamentary appendages on the prosoma; vesiculæ seminales
very large, reflected at their ends, extending across each side of the
stomach. Penis rather small, coloured purplish, with numerous little
tufts of bristles.