REPTILIA. 



47 



of the skeleton ally them to the Monotremes, and some zoologists 

 find in them the ancestors of the marsupial mammals of the 

 Triassic. 



Some of these reptiles resemble turtles in the shape of the 

 head, and the horny beak, replacing teeth ; others had a pair of 

 maxillary tusks ; while still others had a division of teeth an- 

 ticipating the dentition of carnivorous mammals. The last group 

 forms Owen's order, Theriodontia. The order Anomodontia of 

 some authors includes the two former groups. 



No. 67. [278] Dicynodon lacerticeps, Owen. 

 Skull (cast). This singular 



reptile, hitherto found only in 

 the Trias of South Africa, ex- 

 hibits in the modifications of the 

 skull, characters of the Crocodile, 

 Tortoise and Lizard. It has the 

 occipital of the first, the short, 

 round head of the second, and 

 the separated nasal apertures of 

 the last. The cranium is com- 

 pressed in front as in the Lizard, and the occipital condyles have a similar 

 form. The only teeth are two pointed tusks growing downwards from the 

 upper jaw; the lower jaw was armed, like the Tortoise, with a sheath of horn. 

 This specimen, found near Fort Beaufort, Cape Colony, is in the Museum of 

 the Geological Society of London. Size, 6x4. 



ORDER ICHTHYOPTERYaiA. 



As indicated in the name of the order, and of the type genus, 

 described below, these reptiles have some fish-like characters. In 

 general form and in their predatory pelagic habits they much 

 resembled the whales, which replaced them. They are confined 

 to the Mesozoic, and abound especially in the Jurassic of Europe. 

 No true Ichthyosaur has been found in America, but an allied 

 toothless form, with six digits in all extremities, has been found 

 in the Jurassic of Wyoming. It is named Bajptanodon (Saur- 

 anodon). 



Some specimens have a length of forty feet, but many were 

 only a few feet long. The teeth are placed in grooves, and may 

 number two hundred. The eye-orbits are immense, sometimes 

 fifteen inches in diameter, and the eye was protected, and possibly 

 focussed, by a ring of sclerotic plates. 



Their petrified excrements known as " coprolites " consist of 

 bony fragments of fishes and other marine animals. 



