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.
CHELONIA.
The Bridger beds have yielded a great abundance and variety of land, marsh, and fresh-water chelonians. They present much variation of form and size; and, owing to the great pressure in the strata, scarcely any two specimens of the same species are alike; occasionally, however, an undistorted specimen is obtained.
The most abundant remains of turtles are those of a species of the recent genus Emys, which are found in all the beds, and are, perhaps, the commonest fossils of the basin. The genera Trionyx and Hadrianus (Testudo, Leidy) follow next in order.
HADRIANUS, Cope.
Resembles Testudo in form, but has two analscuta, as have most Emydidæ.
Hadrianus allabiatus, Cope.
U. S. Geol. Survey of Territories, 1872, p. 630.
Represented by two ungual phalanges which resemble the claws of Testudo, but are proportionately shorter, broader, and not so pointed at the ends. They are oval in section, both longitudinally and transversely; the articular faces are deep and subinferior.