ORDER IV 



SAUBOPTERYGIA 



177 



stouter. Probably both were invested with a cartilaginous membrane, as in Ichthyo- 

 saurs. The pubes are relatively large, with convex anterior and notched posterior 

 margin, but not pierced by a foramen. They meet, as do also the much smaller ischia, 

 in a long median symphysis. The 

 ilium is slender, and articulated only 

 with the ischium. 



Several nearly perfect skeletons of 

 Plesiosaurus are known from the 

 Lower and Upper Lias of England 

 and Germany, and supposed fragments 

 are known from the Rhaetic. The 

 typical species, P. dolichodeirus, Cony- 

 beare, from the Lower Lias of Lyme 

 Regis, England, attains a total length 

 of 3 m. Other species from the same 

 locality are P. hawkinsi, P. rostratus, 

 and P. macrocephalus, Owen ; and P. 

 conybearei, Sollas, the latter sometimes 

 attaining a length of 5 m. Beautiful 

 skeletons are preserved in the British 

 and Berlin Museums. Several North 

 American species have been referred 

 to this genus. 



E retmosaurus, Seeley. Cora- 

 coids truncated anteriorly, and not 

 extending in front of the glenoid 

 cavity for the humerus. Scapulae 

 extending downward and inward 

 so as to become fused with each 

 other and also with coracoids in 

 the median line. ( Navicular arch 

 degenerate. Lower Lias ; Eng- 

 land. 



Rhomaleosaurus, Seeley. B. 

 cramptoni, Carte sp. Coh/mbosaurus, 

 Muraenosaurus, Seeley. Upper 

 dura ; England. 



Cryptoclidus, Seeley. Resembles 

 Plesiosaurus, except that the ribs 

 are all single-headed, and pectoral 

 arch is like that of Eretmosaurus, 

 Elasmosaums, etc. Upper Jura ; 

 England. 



Cimoliasaurus, Oligosimus, Brimo- 

 saurus, Leidy ; Piptomerus, Oropho- 

 saurus, JEmbaphias, Polycoti/lus, JJronautes } Cope; Trinacroirierum, Cragin ; Maui- 

 saurus, Hector. These genera from the Upper Cretaceous of North and South 

 America and New Zealand are for the most part yet insufficiently characterised, 

 and include very diverse forms. The first-named is also European. 



Pliosawrus, Owen (Ischyrodon, Thaumatosaurus, v. Meyer; Peloneustes, Lydd. ; 

 Lioplewodon, Sauv.), (Fig. 281). Gigantic Plesiosaurs with relatively large 

 VOL. II N 



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W® 



^4M / w^ 



Fig. 280. 



Plesiosaurvs dolichodi irus, Conyb 

 Regis; Dorsetshire. Skeleton, 

 Hawkins). 



Lower Lia 



ventral aspect, ] 



lis 



Lyme 

 (after 



