258 THE OSTEOLOGY OF THE REPTILES 



usually more reduced; frequently hyperdactylate. Teeth inserted in 

 grooves. Face longer. 



Upper Triassic to Upper Cretaceous. Ichthyosaurus Koenig 

 {Proteosaurus Howe), Europe, Asia, Africa, Australia, New Zealand, 

 South and ? North America. 



A widely distributed genus as it is ordinarily accepted. It pre- 

 sents, however, numerous minor modifications that might justify its 

 division.^ 



Family Ophthalmosauridae. Differs from the more typical Ich- 

 thyosauria in the more reduced teeth, the presence of three epipo- 

 dial bones in the front paddles, the more reduced hind paddle, the 

 fusion of the ischium and ilium, in the apparent entire absence of 

 chevrons, and in the more discoidal form of the phalanges. 



Upper Jurassic. Ophthalmosaurus Seeley {? Baptanodon Marsh), 

 Europe and North America. 



Cretaceous (Upper Greensand) . ? Ophthalmosaurus Seeley. 



? ORDER 0MPHAL0SAURIA2 



Family Omphalos auridae. Marine reptiles with a short, shell- 

 crushing skull. Mandibles short, the dentaries united in a strong 

 symphysis, their broad, convex, superior surface beset with several 

 rows of low-crowned, button-like crushing teeth, the largest about 

 fifteen milUmeters in diameter. Vertebrae amphicoelous. "Palate 

 plesiosaur-like." Skeleton otherwise unknown. 



The incompletely known remains of these reptiles, described by 

 Merriam, are very suggestive of a new type of shell-eating aquatic 

 reptiles, but until more is known they are merely suggestive, the 

 ordinal rank and relationships provisional or conjectural. In them- 

 selves the characters are not of ordinal rank, but their associations 

 and their age make it not at all improbable that when fully known 

 they will justify the rank provisionally given to them. From essen- 

 tially the same horizon in Spitzbergen similar teeth have been 

 described by Wiman, which seem to pertain to the same kind of 



1 [Von Huene (1922) divides the old genus Ichthyosaurus into several phyletic lines, 

 the evolution of which he traces from the Triassic to the Upper Cretaceous. — Ed.] 



- [Recent authors (von Huene, Nopcsa) class the Omphalosauria with the Ichthyo- 

 sauria. — Ed.] 



