CIMOTJOSAURUS RICHARDSOXI. 179 



He restricts PIe*io*aurtts proper to those whose scapulae do not 

 meet in the median line throughout their whole extent from the 

 upper to the lower margin, but diverge anteriorly about half-way 

 down. The scapulae are rod-like, small, and narrow, and Avidely 

 separated from each other, resting diagonally upon a long plate 

 (nmostemuni), which is wedged into the coracoid at its summit, 

 taking the place of the clavicle of mammalia and of some reptiles. The 

 anterior portion of each scapula lies at right angles to the dorsal 

 portion, which has a long projection. Cimoliosaurus, on the other 

 hand, has large, broad scapulae, which meet at the median line 

 throughout, and are in the same plane with the eoracoids, forming 

 with these one shield-like plate. The size and strength of the 

 scapulae do not require the supporting bone oinostemum of 

 Plesiosaurus. The dorsal plates, as with the Plesiosaurus, are at 

 right angles to the ventral, but differ in being short and narrow. 

 Mr. Lydekker, finding the fossil possesses all the characters refer- 

 able to Cimoliosaurus, gives it a place in that genus. It is, 

 however, specifically distinct from C. plicatus, Phil., the only other 

 known Oxford clay member of the family, and to which I referred 

 it in vol. ix. of " The Proceedings." Among the other distinc- 

 tive characters already described, the cervical vertebrae are shorter 

 with flatter, terminal faces, and about 31 in number instead of 

 44 as in plicatus. Mr. Lydekker names it Cimoliosaurus ricJiardsoni 

 after its fortunate discoverer. Plesiosaurus proper is restricted 

 to the Rhsetic and Liassic beds, while Gimoliosanrus extends 

 vertically from the Inferior Oolite to the Upper Chalk inclusive. 



