AND AVES OF NORTH AMERICA. 



41 



oliasaurus, the supposed caudals of the latter proving- to be its cervicals. Characters dis- 

 tinguishing it from. Plesiosaurus have never been pointed out, and it is here retained apart, 

 from it on the supposition that its scapular arch is constructed on the same principle as 

 that of Elasmosaurus, a point, however, which has not been ascertained. 



This genus is not as well known as Elasmosaurus, owing to the fragmentary condition 

 in winch it is usually found. Its marked character is its short depressed cervical region, 

 as compared with the excessively long and compressed one of Elasmosaurus. It also dif- 

 fers from it in the apparent continuity of the series of diapophyses from the dorsal to the 

 cervical series. In Elasmosaurus these processes are wanting on the anterior dorsals. 

 They are very elongate on the other hand, on the posterior dorsals of Elasmosaurus ; in 

 Cimoliasauriis we have as yet no evidence as to their length, as they arc broken in our 



specimens. 



Ki- 



ns. 



Fie. 14. 



Fie. 10. 



/-^>::::l 



The rapid diminution in dimensions of the cervical scries in Cimoliasauriis indicates 

 a short neck, and far less slender general form. Eeidy suggests from the absence 

 of sacral characters, that posterior limbs have been probably wanting in this genus: the 

 same vertebral characters are seen in Elasmosaurus, but it has a large pelvic; and scapular 

 arches; (be presence of limbs in it cannot be doubted. The femur of Cimoliasauriis is 

 described below, and is the only limb bone yet assignable to a species of this genus. It 

 resembles that of Plesiosaurus. It is thicker and shorter however than in any species of 

 the latter genus, and is quite short. The distal extremity is thick, and presents pits for 

 the attachment of the articular cartilage 1 ; the laces for both ulna, and radius arc extensive, 

 and indicate a large maims and elongate limb. The rotundity of the head indicates ex- 

 tensive rotation ; and we may be satisfied that the animals of this genus were furnished 



A.MERI. PHILOSO. SOO. — VOl,. XIV. 1 I 



