326 



[December, 



Measurements of the largest dorsal vertebra. 

 Length of body, ..... 23 



(( 



at articular faces, 



inches. 



4i ' 

 3i 

 2 lines. 

 1 inch, 

 li " 

 1 



mbar vertcbrn. 



2 inches. 

 2! 



2 in. 10 lines. 

 2i lines. 



Breadth 



Heighth 



Depth of articular faces, 



Length of transverse processes, 



Diameter " *' 



Breadth of spinal canal, 



Measurements of the smallest In 

 Length of body. 

 Breadth 

 Heighth ' 

 Depth of articular surfaces, 



DiscosAURus vETusTus, Leiily . A saurian founded upon a single vertebra 

 with the processes broken away, obtained by Mr. Joseph Jones from the creta- 

 ceous formation of Alabama. 



The body is about as large, and has a general resemblance to that of Plesio- 

 saurus pachyomus, Owen, ropreseuted in fig. 3, tab. xx., of the Monograph on the 

 fossil reptiles of the Cretaceous Formation. It differs most remarkably from the 

 vertebral bodies of Plesiosaurus, in the articular faces forming distinct concave 

 disks, separated from the body by a constriction or short neck. The body is 

 relatively much broader in relation to its length than in Plesiosaurus. The spe- 

 cimen is a cervical vertebra. Upon eaeh side it has a deep, concave, transversely 

 oval, costal pit, with a very prominent, sharp border. 



Measurements, 

 Length of body. 

 Breadth 

 Heighth 



Depth of articular surfaces, . 

 Transverse diameter of costal pit, 

 Vertical 



Depth of costal pit, . 



The fragment of a vertebra described by Dr. Dekay in the Annals Lyceum of 

 Nat. Hist, of New York, Vol. 3, p. 165, and represented in PI. 3, fig. 11, from 

 the Green Sand of New Jersey, and observed by that gentleman to be allied to 

 the Plesiosaurus, probably belongs to the Discosaurus vetustus. 



The vertebra described by Dr. Harlan in the Journal of this Academy, Vol. 4, 

 p. 232, and represented in pi. xiv. fig. 1, was referred to the Plesiosaurus. The 

 specimen was from the Green Sand of New Jersey, and is preserved in the cabi- 

 net of the Academy. It does not belong to a saurian, but is a posterior dorsal 

 vertebra of a cetacean allied to the Delphinus. The vertebral body is relatively 

 twice the length of what it is found to be in the latter. The transverse process 

 is also relatively short and broad; at its extremity it has an articular facet for the 

 head of a rib. 



The vertebra is probably the type of a form existing in a distinct genus of 

 ancient Cetacea, for which I propose the name Priscodklphinus. The species I 



