266 SATJKOPTEEYGIA. 



2080*. An imperfect dorsal vertebra ; from Street. In its ventral 

 aspect this specimen closely resembles the dorsals of the 

 skeleton No. 2020*. The dimensions of the centrum are : 

 —length 0,025 (0-96 inch), height 0,033 (1-3 inches), 

 width 0,039 (1*54 inches). The distinctly cupped centrum 

 and low and broad neural canal are well seen. 



Hawkins Collection. 



R. 654. An entire late dorsal vertebra of similar general type ; 

 from Lyme-Regis. In general characters this specimen 

 agrees very closely with the detached dorsal in No. 2022*, 

 but the neural spine is taller, exceeding twice the height 

 of the centrum, and thus resembles the unnamed skeleton 

 No. R. 1329. Presented by J. E. Lee, Esq., 1885. 



43061. Slab showing the posterior aspect of a crushed dorsal 

 vertebra of similar type : from Lyme-Regis. The height 

 of the arch and spine is about two and a half times that 

 of the centrum. Purchased, 1871. 



2039*. Slab showing the ventral aspect of a mandible not improbably 

 belonging to this species ; from Street. This specimen 

 agrees approximately with the mandible of No. 2022*. 



Hawkins Collection. 



Plesiosaurus macrocephalus, Owen x {ex Conybeare). 



Syn. Plesiosaurns brachyceplialus, Owen 2 . 



Of comparatively large size, the length of the skeleton of the type 

 of P. brachyceplicdus being 10 feet 6 inches. Skull relatively large, 

 wide posteriorly, but with the premaxillary region much narrowed, 

 its length being contained about two and a half times in the interval 

 between the atlas and the pectoral girdle. Neck short, with some 

 30 vertebrae 3 ; cervicals short, with the upper costal facet in 

 immature specimens confluent with the facet for the arch ; terminal 

 faces slightly cupped, and haemal aspect with very slight ridge; 



1 Eep. Brit. Assoc, for 1839, p. 62 (1840), and Trans. G-eol. Soc. ser. 2, vol. v. 

 pt. 3, p. 515 (1840, read 1838). 



2 Eep. Brit. Assoc, for 1839, p. 69 (1840). 



3 Owen gives the number of cervicals in P. macrocephalus as 29, and states 

 that at least 28 are cervical in P. brachycephalus. Sollas (Quart. Journ. Geol. 

 Soc. vol. xxxvii. p. 479) states that in the latter the 29th is certainly cervical, 

 and that the 30th and 31st are probably also referable to the neck. In the type 

 of the former there is no reason why there should not be a similar number of 

 cervicals, since the sides of the 30th and 31st vertebrae are not exposed. 



