Page:The Osteology of the Reptiles.pdf/276

258 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 presents, however, numerous minor modifications that might justify its division.

. Differs from the more typical Ichthyosauria in the more reduced teeth, the presence of three epipodial 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.

. 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 millimeters 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 themselves 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 essentially the same horizon in Spitzbergen similar teeth have been described by Wiman, which seem to pertain to the same kind of