22 DISCOSAURTJS. 



DISCOSAURUS. 



Diiiicosaiiriis vetustii!^. 



Discosaurus vctustus, Leidy, Proc. Acad. Nat. Sci. Phila. 1851, 326. 



The remains of a large Saurian, apparently nearly related to the Plesiosaurus of 

 Europe, discovered in the American Cretaceous deposits, have occasionally come 

 under my notice. Dr. Harlan has described and figured a vertebra, obtained, 

 together with several others, from Mullica Hill, N. J., which he referred to the 

 Plesiosaurus? The specimens, upon which this view was foimded, are preserved 

 in the museum of the Academy of Natural Sciences, and prove to belong to a 

 Cetacean, of the Dolphin family. Subsequently Dr. DeKay described and figured 

 a fragment apparently of a cervical vertebra, from the Green-sand of New Jersey, 

 evidently belonging to the Saurian to which I allude, and which he recognized as 

 being allied to Plesiosaurus.^ 



The collection of the Academy of Natural Sciences contains a few remains of 

 the Saurian indicated from four different localities, as follow : — 



1. The mutilated bodies of two caudal vertebrse, as I suppose them to be, from 

 the Cretaceous deposits of Alabama, presented by Prof. Joseph Jones, of Georgia. 



The specimens, represented in Figs. 4, 5, 6, Plate V, have the body in the form 

 of a transverse section of a cylinder, compressed from above downward, with the 

 sides and under part slightly narrowed towards the middle. The articular extremi- 

 ties are transversely elliptical and moderately concave, but have prominently convex 

 borders. They are constricted or defined from the rest of the body by a narrow 

 groove, which gives them the appearance of distinct plates or disks applied to and 

 terminating the body. From this peculiar appearance, the name of Biscosanriis was 

 proposed for the genus to which the vertebra; belong. At the under part of the 

 body, as seen in Fig. 5, the groove is inflected on each side apparently with the view 

 of producing facets for a chevron bone. It is this apparent adaptation of the parts 

 to the articulation of chevron bones which has led me to consider the vertebrae uuder 

 consideration as caudals, otherwise from their resemblance to the cervical vertebrae 

 of Plesiosaurus pachyonms, as represented by Prof. Owen,^ I should have viewed 

 them as belonging to the cervical series. 



Between the position of the inflections to accommodate the chevron bones, the 

 under part of the Ijody forms a pair of feeble ridges, the intervening surface of which 

 presents on one side a single venous foramen communicating by a branching vertical 

 canal with the spinal canal. The latter, in both specimens under examination, is too 

 much broken to judge of its form, and no other information is to be ascertained from 

 the abutments of the vertebral arch other than that they were completely coosified 

 with the body. The side of the body is produced into a large conical protuberance 



' .Tourn. Acad. Nat. Sci. Tliila. IV, 1824, 232, pi. xiv, fig. 1; Med. Phys. Res. 1835, 382. See 

 note, page 1, of this Memoir. 



» An. Lye. Nat. Hist. New York, III, 1828, 165, pi. iii, fig. 11. 

 ' British Fossil Reptiles, Eualiosauria, pi. 28. 



