PLESIOSATJRID-E. 235 



vertebrae marked by distinct plications, which are especially promi- 

 nent in immature examples. Humerus (fig. 71) articulating dis- 

 tally with only the radius and ulna ; the former being elongated 

 antero-posteriorly, and the latter comparatively short and wide ; 

 and there being a distinct interval between the two. In the humerus 

 and femur the pre- and postaxial rough surfaces for cartilage at 

 the distal extremity extend to an equal height. 



This species was founded upon two imperfect cervical vertebrae 

 (No. E. 1332), from the Oxford Clay. 



The adult but somewhat crushed skeleton on which Murcenosaurus 

 leedsi was founded (infra, No. E. 1262) has cervical vertebrae of the 

 same type. In that skeleton the pectoral arch is very imperfect, but 

 another example, in the collection of A. N. Leeds, Esq. (No. 22), 

 shows the bony bar connecting the ventral plates of the scapulae 

 with the coracoids ; it appears that in the restoration given by 

 Seeley in the ' Quart. Journ. Geol. Soc' vol. xxx. p. 448, the dorsal 

 portion of the scapula has been mistaken for the ventral plate \ The 

 name Plesiosaurus infraplanus was applied to three centra of imma- 

 ture cervical vertebrae obtained from Brill, Stanford (Berkshire), and 

 Shotover ; at least the two first being certainly from the Oxford 

 Clay, although described by Phillips among the Kimeridgian forms. 

 These vertebrae are identical with cervicals of an immature skeleton 

 (infra, No. E. 1282) in the collection of Mr. Leeds. Plesiosaurus 

 hexagonaUs was founded upon a caudal vertebra from Cowley, which 

 appears to be also of Oxfordian age, and is probably referable to the 

 present species. It has been mentioned above (p. 209) that the 

 pectoral girdle and limb, together with the dorsal vertebrae, figured 



1 See Geol. Mag. dec. 3, vol. v. pp. 351-352 (1888). The accompanying 

 woodcut shows Seeley's restoration of the pectoral girdle ; the bones marked s, 



Restoration by Seeley of the pectoral girdle of Cimoliosaurus plica t 'us. 



and made to meet in the middle line, being the dorsal portions of the scapula-, 

 which should really be widely separated ; the median production of the coracoidl 

 (c) has been broken away. 



