AND AYES OF NORTH AMERICA. 



75 



IIOLOFS OBSCURUS, Leidy. 



Thoraaosaurus obscurua, Cope, (tool. Surv. N. J., App. C. Crocodilus obacurua, Leidy, Smithson. Contrib., 1865, 

 p. 115. Tab. II, fig. 4. Undetermined crocodile; teeth tab. I, f. 7, 8, I). 



This species was established by Prof. Leidy on vertebrse from Barnesboro, Gloucester Co. and Arneytown, Bur- 

 lington Co., New Jersey. 1 have procured numerous vertebrae from the former locality, which were associated with 

 a cranium, which was nearly destroyed before reaohing my hands. Enough, however, has been preserved to indicate 

 with certainty that it is agavial, 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 oertainly to be 

 ascribed to the T. obscurusthan to the T. tenebrosus, of which several portions were discovered in the same excav- 

 ations. 



The vertebrse from Barnesboro in my possession have apparently pertained to two individuals ; two cervicals, a 

 second and lil'IJi dorsal, with six other dorsals and lumbars and a, caudal, of the one, and a first and lif'th dorsal with 

 eleven oilier dorsals and lumbar vertebrae, of the oilier individual. 



In addition to these, I have examined two cervicals found with muzzle and long hones at Barnesboro; a, line 

 series of vertebra and oilier hones in the Museum of the Academy from near Birmingham ; three line series in 

 possession of Prof. G. II. Cook.f the Mount Holly Lyceum Natural History, and Prof. 0. C. Marsh of Yale College, 

 all from Birmingham ; portions of two individuals in my own collection from the same place, and a set of eight verte- 

 brse from Mullioa Hill in my possession. Numerous other specimens of this species have fallen under my examination. 

 I lence ii, is obvious that t Ids is the most abundant gavial of the New Jersey Cretaceous. 



A series of cervicitis 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 oonoave below, since the parapophyses descend much below the plane of the centrum, 

 and are united by an arched connection in front, which is not separated from the rim of the cup. As usual the para- 

 pophyses oontinue to rise, till on the sixth they are a little above the plane of the centrum. They also beoome more 

 posterior, fill on the sixth their centre is opposite the middle of the centrum without ball: on the seventh this 

 point is behind the middle, 'the iirst, 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 fra.ee of median inferior keel exists ; it is quite strong, but thin and concave on the fifth, 

 while <.n 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 hypapophysi* 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 arc similar but stronger. On the 



seventh if is much more elevated, the groove between its halves being now it transverse plane. On the first dorsal it 

 is a simple, large process, extending over half the centrum with it 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 bice 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 scries, ■which show many of these vertebra. 



The oups Of the third to fifth cervicitis look it little more I runcalc below, owing to the prominence of the trans- 

 verse ridge. They art! 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 I lie 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 scries first mentioned as from I'.arnesboro presents typical characters of the cervical hypapophyses. 



t The types of T. obscurus preserved in the museum of Kutgers College have been kindly placed in my hands by John Smoot, Asst. State Ueologijt. 



