44 THE EXTINCT BATRACHIA, KEPTILIA 



green saud of New Jersey, described previously in the Proceedings of the Academy of Natural Sciences, but in that 

 the large transverse process is cylindrical, while it is compressed cylindroid in the Ark. saurian, and probably the 

 latter belongs to a distinct genus, for which the name Brimosaurus is proposed. The bones are imbedded in a hard 

 limestone with mollusca, and they probably belong to the cretaceous or to the eocene period. One of the most perfect 

 of the vertebras presents the following measurements : 



Inches. 

 Length of the body, 3jj 



Depth articular surfaces, 5 



Breadth do. do., G 



Length of the neural arch, 3 



Dr. Leidy proposes to consider this species as the type of a genus distinct from the present, because its diapophyses 

 are compressed in section, while those of Cimoliasaurus are cylindroid. I think this difference depends on the posi- 

 tion in the vertebral column. These processes descend on the anterior part of the column and become more flattened, 

 until they resemble diapophyses of ordinary cervicals. This vertebra therefore was an anterior dorsal. 



ELASMOSAURUS, Cope. 



Leconte's notes on Geology of the route of the Union Pacific Railroad, 1868, p. 08. Cope, Proceed. Acad. Nat. 

 Sciences, 1868, p. 92. 



This genus has been more completely preserved to us than any other American repre- 

 sentative of the order, and hence may be accepted as most clearly expressive of its char- 

 acters. In the interpretation of these, however, considerable difficulty has been experi- 

 enced, as the structure form appears, at first sight, to reverse to a remarkable degree, 

 the usual proportions of known reptiles. 



The determination of the anterior extremity of the vertebral column has been rendered 

 certain by the fortunate completeness of the cervical series, as the extraordinary length 

 of the latter, equalling three times that of the body, renders the most careful scrutiny 

 necessary. 



The neural arches are every where continuous with the centra, without sign of suture, 

 and are externally plane. The neural canal is exceedingly small for the size of the 

 vertebrae, especially on the lumbars and caudals. 



The dorsal vertebras are remarkable from the fact that the diapophyses disappear on 

 the anterior part of the series, and gradually diminish in length from behind forwards to 

 the point of disappearance. On the median and posterior parts of the series they are 

 very elongate, and rise for a short distance from the basis of the neural arch. Ante- 

 riorly, they descend and shorten, and finally remain only as the slightly elevated borders 

 of rib-pits. Throughout the whole of the anterior portion of the column to the cervicals, 

 the neural spines are of great elevation, and of such antero-posterior extent as to be 

 nearly continuous. 



The cervical vertebra? are not only more numerous, but become anteriorly much smal- 

 ler and more attenuated than in its allies of the same family. They are remarkably com- 



