Page:Synopsis of the Exinct Batrachia and Reptilia of North America. Part 1..pdf/81

 AND AYES OF NORTH AMERICA. 75 IIOLOPS OBSCURUS, Leidy. Thoracosaztrus obseurut, Cope, Geol. Surv. N. 3., App. C. Crocodiles obscurus, Leidy, Smithson. Contrib., 1S65, p. 113. Tab. II, 11g. 4. Undetermined crocodile; teeth tab. I, f. 7, 8, 9. This species was established by Prof. Leidy on vertebra from Barnesboro, Gloucester Co. and Arneytown, Bur-lington Co., New Jersey. I have procured numerous vertebrae from the former locality, which were associated with a cranium, which was nearly destroyed before reaching my hands. Enough, however, has been preserved to indicate with certainty that it is a gavial, and probably of the same genus as that to which Cook's Monmouth County skull belonged. Numerous dermal plates were procured at the same time, which however are not more certainly to be ascribed to the T. obscures than to the T. tenebrosns, of which several portions were discovered in the same excav-ations. The vertebrae from Barnesboro in my possession have apparently pertained to two individuals ; two cervicals, a second and fifth dorsal, with six other dorsals and lumbars and a caudal, of the one, and a first and fifth dorsal with eleven other dorsals and lumbar vertebne, of the other individual. In addition to these, I have examined two cervicals found with muzzle and long bones at Barnesboro ; a fine series of vertebra and other bones in the IlIuseum of the Academy from near Birmingham ; three fine series in possession of Prof. G. H. Cool:,{ the Mount Holly Lyceum Natural History, and Prof. 0. C. Marsh of Yale College, all from Birmingham ; portions of two individuals in my own eolkction from the same place, and a set of eight verte-brae from Mullica Hill in my possession. Numerous other specimens of this species have fallen under my examination. Hence it is obvious that this is the most abundant gavial of the New Jersey Cretaceous. A series of cervicals from Birmingham is instructive, showing the differences in the characters of the respective vertebra', The axis, which as usual is coossified with part of the body of the atlas thereby much increasing its length, has parapophyses represented by two crests directed downwards and separated by a deep longitudinal cavity; they are united in front. An obtuse ridge on the side of the centrum separates two longitudinal concavities. The third cervical is also deeply concave below, since the parapophyses descend much below the plane of the centrum, and are wilted by an arched connection in front, which is not separated from the rim of the cup. As usual the para-pophyses continue to rise, till on the sixth they are a little above the plane of the centrum. They also become more posterior, till on the sixth their centre is opposite the middle of the centrum without ball : on the seventh this point is behind the middle. The first dorsal is readily distinguished by the small size and posterior direction of the articular face of this parapophysis ; its middle is a little below opposite the middle of the cup. On the third dorsal the same point is just above opposite the middle of the cup. On the fourth cervical a trace of median inferior keel exists ; it is quite strong, but thin and concave on the fifth, while on the sixth it is thicker, and does not separate deep concavities, but only slightly concave planes. It is still more elevated on the seventh, and increases beyond. On the third there is no distinct hypapophysis. On the fourth, a transverse elevation on the anterior arch connecting the parapophyses marks it ; on the next it appears in the same place as two small longitudinal tubercles with groove between. On the sixth they are similar but stronger. On the seventh it is much more elevated, the groove between its halves being now a transverse plane. Onethe first dorsal it is a simple, large process, extending over half the centrum with a small knob behind it : on the third it has a longer base, but on the second the longest, extending the whole length of the centrum. On the fifth it is thick, with rounded edge below, and with a truncate triangular face in front. It is apparent on the eighth, as an obtuse eleva-tion in front. From the fourth posteriorly the characters are drawn from other series, which show many of these vertebra,. The cups of the third to fifth cervicals look a little more truncate below, owing to the prominence of the trans-verse ridge. They are almost perfectly round thence to the second dorsal, where the transverse diameter begins to exceed the vertical a little. First on the fifth dorsal the cup assumes some of the narrowed form of the centrum. The very numerous lumbars present nothing peculiar. As in other species they are more or less striate grooved at the bases of the cups and balls. The series first mentioned as from Barnesboro presents typical characters of the cervical hypapophyses. t The types of T. obscures preserved in the museum of Rutgers College have been kindly placed in my bands by John Smock, Asst. State Geologist.