A small reptile represented by sixteen vertebræ and a portion of the
pelvis.
The _cervicals_ have short centra, with very deep articular cups
and hemispherical heads: the latter have a prominent rim around the
base. The hypapophyses are short, stout, and very nearly vertical
in direction; the sides of the centra are channelled by a deep
vertebraterial canal; the parapophyses are developed very low down,
and are very prominent. The diapophyses are developed partly from the
centra and partly from the neurapophyses; they are stout and very
short. The facets for the ribs are developed in the usual place.
The neural arch is rather high, and forms a small, narrow canal;
the proportions of the neurapophyses and neural spines are about as
in _Alligator mississippiensis_, but the zygapophyses are not so
prominent.
The _dorsals_ show a considerable increase in size over the
cervicals; the centra become elongate, and the articular cups
shallower and transversely oval. Several of the anterior vertebræ
retain large hypapophyses. In the dorsal region the diapophyses are
developed from the neurapophyses alone, and at a considerable height
above the neuro-central suture; they are long and depressed. The
zygapophyses and neural spines present no peculiarities of structure.
In the _lumbar_ region the vertebræ regain their cylindrical form,
and become still more elongate; but the cups are comparatively
shallow and the heads low; there is no distinct shoulder. The
neural canal is small, with low, broad neurapophyses, from which
are developed very broad and depressed diapophyses, which project
outwards in a horizontal plane. The neural spines are thick, and
broad antero-posteriorly, but are so broken that their height cannot
be determined.
In both dorsal and lumbar region the neurapophyses are deeply notched
on their posterior edges, and close to the neuro-central sutures, for
the passage of the spinal nerves.
The _ilium_ is very high compared with most crocodiles; its vertical
diameter is considerably more than half of the antero-posterior
diameter. The construction of the bone is very much like that in the
modern _Crocodilia_; but the suprailiac border is more regular, and
the anterior tuberosity is not so thick or so much everted as in
these forms. The acetabulum is small, shallow, directed downwards
and outwards, and situated considerably forward of the median line.
The iliac surface is smooth, but very irregular, being very deeply
concave above the acetabulum, and convex behind it. The sacral
surface is rugose, rises above the sacrum, and shows attachments for
two sacral vertebræ. Thus the construction of the entire pelvis shows
but very little variation from the modern type.
_Measurements._
M.
Antero-posterior diameter of ilium ·095
Vertical diameter of ilium ·061
Antero-posterior diameter of acetabulum ·029
Length of centrum of third (?) cervical vertebra
(from edge of cup to tip of ball) ·032
Height of neural canal, third (?) cervical ·0095
Length of hypapophysis of third cervical ·0085
Length of centrum of a posterior dorsal ·040
Length of diapophysis (about) ·032
Length of centrum of a lumbar ·046
Vertical diameter of a lumbar ·029
Breadth of neurapophysis of a lumbar ·027
Crocodilus heterodon, Cope.
_Alligator heterodon_, Proc. American Philosophical Society, 1872, p.
544.
Represented by a single tooth from the posterior part of the
mandibular series. It agrees very closely with the corresponding
tooth of _Alligator mississippiensis_, but presents some differences.
The crown is very low, obtuse, and finely striate; it is compressed
and shows a cutting-edge. Its longest diameter is fore-and-aft; both
this and the transverse diameter are proportionately greater than in
the modern species. The constriction of the neck is very decided; the
fang is large, and especially thick.
_Measurements._
M.
Fore-and-aft diameter of crown ·010
Transverse diameter of crown ·007
Vertical height of crown
Crocodilus clavis, Cope.
U. S. Geol. Survey of Terrs. 1872, p. 612.
This species is indicated by the remains of a crocodilian larger
than _Crocodilus Elliotii_, but very different from it. The pitting
of the dermal scutes, and of all the cranial bones, is deeper than
in any other of the Bridger crocodilians in our possession, and very
strongly resembles that in _Alligator mississippiensis_.
The _mandible_ has a long symphysis, and the alveolar border shows
the sudden deep depression just behind it, which is so marked in
the ordinary alligator. The rami, however, do not diverge at such an
open angle. The jaw is very stout, and is deeper and thinner than
in _Crocodilus Elliotii_; and is of about the same proportionate
thickness, but deeper than in the alligator. The splenial ends
obtusely, and approaches the symphysis somewhat more closely than in
the alligator, but does not enter into its formation. The teeth are
stout and obtusely conical, not striate, and implanted very close
together; they exhibit about the same alternation of size as do
those of the alligator. What appears to be the canine is small; it
is preceded by a much smaller, and succeeded by a slightly smaller
tooth. The dermal scutes are quadrate in shape; they are deeply and
irregularly pitted, and have a low but distinct longitudinal keel;
they are suturally united by their lateral borders.