ICHTHTOSAURID^:. 9 



Ophthalmosaurus (?) cantabrigiensis, Lydekker l . 



Typically of small size. The three distal facets of the humerus 

 nearly equal in size ; and the antero-posterior diameter of the 

 proximal extremity of the same bone exceeding that of the distal. 

 This species may belong to Baptanodon. 



Hab. Europe (England). 



43989. The right humerus; from the Cambridge Greensand. 



{Fig.) The type specimen (woodcut, fig. 6). The general contour 

 of this bone is very similar to that of the much larger 

 humerus of 0. icenicus, but the proximal extremity is 

 larger than the distal, and the facet for the pisiform is 

 nearly equal in size to that for the radius. 



Purchased, 1872. 



Some, or all, of the following specimens mag be specifically 

 distinct. 

 35348. The imperfect right humerus of a much larger individual ; 

 from the Cambridge Greensand. The radial portion of the 

 distal surface is broken away ; and the facet for the pisi- 

 form is double, as if for the articulation of a fourth bone. 



Purchased, 1859. 



35310. An imperfect bone, which is probably a humerus ; from the 

 Cambridge Greensand. The three distal facets, although 

 somewhat worn, are distinctly visible. Purchased, 1859. 



Ophthalmosaurus icenicus, Seeley 2 . 



The type species. Larger than the type of the preceding species, but 

 the vertebrae considerably smaller than those of Ichthyosaurus trigonus. 

 The postaxial facet on the distal extremity of the humerus smaller 

 than that for the radius ; and the antero-posterior diameter of the 

 proximal extremity of the humerus less than that of the distal 

 extremity. Vertebra? of the same general type as those of Ichthyo- 

 saurus trigonus, but relatively shorter, and in the cervical region 

 with the cupping of the anterior face of the centrum confined to the 

 central portion, and surrounded by a flattened periphery. 



Tho type specimens are from the Oxford Clay (Middle Jurassic), 

 and are figured in the ' Quart. Journ. Geol. Soc' vol. xxx. pis. xlv., 

 xlvi. 



Bab. Europe (England). 



1 Geol. Mag. <lre-. 3, vwl v. p. 310 (1888). 



a Quart. Journ. Geol. Sue. vol. xxx. )>. 696 (1874). 



