CLASSIFICATION OF REPTILES. 51? 
Rhamphorhynchus had teeth in the back of the jaw, the 
ends of the jaws being toothless and probably encased in 
horny beaks, while in Pteranodon the jaws were toothless. 
They were of different size, some expanding only as much 
as a sparrow, others with a spread of about nine metres (27 
feet). They were contemporaries of the Dinosaurs, several 
forms, discovered by Marsh, occurring in the Cretaceous 
beds of Kansas, 
Cuass VI, REPTILIA. 
Air-breathing Vertebrates, with limbs usually ending in claws ; limbs 
sometimes absent, rarely paddle-shaped ; body scaled ; ribs well developed ; 
heart in the highest forms four-chambered ; cold blooded ; an incomplete 
double circulation ; oviparous ; eggs large; embryo with an amnion and 
allantois ; no metamorphosis. 
Order 1. Theromorpha.—Mammal-like saurians with solid pelvis and 
shoulder-girdle, and with canine-like teeth, or toothless 
and beaked. (Dicynodon.) 
Order 2. Sauropterygia.—Extinct colossal saurians, with long necks, 
head of moderate size. (Plesiosaurus, Elasmosaurus.) 
Order 3. Ichthyopterygia.—Head large, orbits large; limbs paddle- 
; shaped ; extinct forms. (Ichthyosaurus.) 
~~ Order 4. Rhynchocephalia.—Lizard-like; vertebre bi-concave, species 
mostly extinct. (Sphenodon.) 
~~ Order 5. Ophidia.—Body long, cylindrical, usually limbless; no shoul- 
der-girdle. (Hutsenia.) 
Order 6. Pythonomorpha.—Extinct, snake-like, limbs paddle-shaped. 
(Mosasaurus. ) 
—~Order 7. Lacertilia.—Body with a long tail; usually four limbs; mouth 
not dilatable, the bones of the jaw being firm. (Sceleporus.) 
— Order 8. Chelonia.—Body enclosed in a thick shell, within which the 
head and limbs can be withdrawn. (Testudo.) 
~ Order 9. Crocodilia.—Thick-scaled; heart four-chambered. (Croco- 
dilus.) 
Order 10. Dinosauria.—Colossal extinct saurians, capable of rising 
and resting on the hind legs, and making three-toed tracks, 
(Hadrosaurus.) 
Order 11. Pterosauria.—Extinct flying saurians, with the fore limbs 
large and a very long ulnar finger; toothed or toothless. 
(Pterodactylus.) 
