PLESIOSAUKID^. 181 



Cervicals with moderately or very short centra, having only single 

 costal facets (fig. 61), and the terminal faces transversely ellipsoidal 



Pig. 59. 



Cimoliosaurus (cf.) trochanter ins. — Diagram of the pectoral girdle ; from the 

 Kimeridge Clay of Ely. Much reduced, s, scapula ; g, glenoid cavity ; 

 c, coracoid. (From the ' Quart. Journ. Geol. Soc.') 



and more or less clipped. Dorsals with forward overhang of 

 upper part of centrum, and the cupping of the faces corresponding 

 to that of the cervicals. Pectoral girdle (fig. 59) with the 

 scapula? very large and having very broad and flat ventral plates 

 meeting anteriorly in the median line, and the dorsal portion very 

 small and narrow ; no omosternum ; coracoids either short and broad, 

 or moderately elongated, usually with a narrow median bar extending 

 forwards to unite with the scapulas l j scapulo-coracoidal foramina 

 large and closed. Pelvis with the ischia (fig. 65) very short and 

 wide. Humerus usually longer than femur, and articulating distally 

 with either two or three bones, which are frequently transversely 

 elongated and lose all resemblance to long bones, the ulna being 

 generally more or less shortened antero-posteriorly and expanded 

 laterally. Chevrons (at least in the typical group) open inferiorly. 



The pectoral girdle is imperfectly preserved or unknown in the 

 English Cretaceous species, in which the length of the neck is fre- 

 quently also unknown. 



This genus is provisionally taken to include all the forms having 

 the above-mentioned type of pectoral girdle, with single costal 

 facets to the cervical vertebra). The type species, C. magnus of 

 the North-American Cretaceous, is noticed below ; Discosaurus 

 has been shown by Cope to be specifically identical, while .there 

 appear to be no grounds for gencrically distinguishing Elasmosaitrus 

 platyurus, Cope 8 . Mauisaurus has vertebra) agreeing precisely in 



1 See Introduction. 



2 Proc. Ac. Nat. Sci. Philad. lor L868, p. 1)3 (1808). There appears to be a 

 confusion of cervicnl with caudal vertebra- in the comparison of this form with 

 Cimoliosaurus. 



