plesiosatjuid^. 25"> 



although somewhat smaller, present a marked resemblance to the 

 undermentioned specimens, which may perhaps belong to the same 

 species. 



Hab. Europe (England and [?] Luxemburg). 



R. 1440. Three imperfect cervical vertebrae, cemented together by 

 matrix ; from the Lower Lias of Barrow-on-Soar, Leices- 

 tershire. The neural spines and portions of the arches 

 are wanting, but there is a natural cast of the neural 

 canal. The dimensions of the centrum of the hindmost 

 specimen are: — length 0,035 (1*38 inches), height 0,032 

 (1-26 inches), width 0,037 (1*45 inches); the correspond- 

 ing dimensions of one of the cervicals of P. dewalquii 

 being 0,024 (0*96 inch), 0,021 (0-83 inch), 0,028 (14 

 inches). Presented by Mrs. B. Etlterldrje, 1888. 



R. 1335. Three larger imperfect cervical vertebras, cemented together 

 by matrix ; from the Lower Lias, locality unknown. The 

 neural spines are wanting, and tho hindermost centrum 

 has been transversely cut and polished. No history. 



B. Typiccd Group. 



Skull either small or comparatively large, with short mandibular 

 symphysis. Cervical vertebras (fig. 80), with the centra of moderate 

 length, having more or less distinctly cupped terminal faces and 

 double costal facets ; neural spines of moderate height or short. 



The characters of the cervical vertebras of this group are such that 

 those of the Coelospondyline group of Cimoliosaurus might well 

 have been evolved from them. 



Plesiosaurus dolichodirus, Conybeare l . 

 Syn. Plesiosaurus cliduchus, Seeley 2 . 



The type species ; of moderate size. Skull small, with a short 

 V-shaped mandibular symphysis (fig. 47, C). Neck very long, the 

 length of the skull being contained about six times in the interval 

 between the atlas and the pectoral girdle. Vertebra) with rugosities 

 at the extremities of the centra. Cervicals some 41 in number, 

 with the centra relatively long, having the costal meets widely 

 separated from the neuro-central suture, the terminal faces slightly 

 cupped, and the hajmal foramina separated by a very slight ridge, 



1 Trans. Gcol. Soc. ser. 2, vol. i. pt. ii. p. 889 (1824). 

 - Ann. Mag. Nat. Hist. ser. o, vol. xvi. p, 350 (1805). 



