ICHTHY0PTERYG1A. 



The three facets at the distal extremity of the humerus and femur 

 are subequal ; and it is possible that some of the English Cretaceous 

 species presenting this character which are referred to Ojohthalmo- 

 saurus may he referable to this genus. 



Genus OPHTHALMOSAURUS, Seeley 1 . 



Teeth present, but apparently small, and perhaps confined to the 

 anterior portions of the jaws. Humerus (fig. 6) and femur with 

 strongly developed trochanteric ridge on dorsal surface, and articu- 

 lating distally with three bones, as in Baptanodon (fig. 5), which are 

 of irregular polygonal contour, the ulna being pentagonal. Clavicles 

 (typically) separate, with the interclavicle wedged in between them. 



Fig. 6. 



Ophthalmosaurus cantabrigiensis. — Dorsal and distal aspects of the right 

 humerus ; from the Cambridge Greensand. \. a, trochanteric ridge ; 

 r, facet for radius ; u, do. for ulna ; p, do, for pisiform. 



Yertebral centra of the general type of those of the Campylodont 

 subgroup of Ichthyosaurus. Coracoid without posterior notch. 

 Humerus and femur apparently (except at the distal end) of the 

 general type of those of Ichthyosaurus campylodon, and relatively 

 large in proportion to the vertebras. In Baptanodon, and probably 

 also in this genus, both pectoral and pelvic (fig. 5) limbs relatively 

 wide, containing six longitudinal rows of phalangeals, and the third 

 digit (or that arising from the intermedium) contains two such 

 rows, with the consequent presence of two centralia. 



1 Quart. Journ. Geol. Soo. vol. xxx. p. 696 (1874). 



