EXTINCT REPTILES. 645 



the paddle the number of digits may be more than five, and the 

 phalanges of each digit are often very numerous. The pectoral arch 

 consists of coracoids, scapulae, clavicles, and a T-shaped episternum, 

 but there is no sternum. The skull has a long tapering rostrum, large 

 orbits, a large parietal foramen, and usually sharp conical teeth in a 

 continuous groove. The vertebrae are deeply amphiccelous. There 

 was no dermal armour. The length of the body is sometimes 30 to 

 40 ft. Some species were viviparous. 



Examples. Ichthyosaurus , Ophthalmosaurus. 

 Pythonomorpha. These strange Cretaceous Reptiles should prob- 

 ably be placed near the Lacertilia and the Rhynchocephalia. They 

 are specially characterised by the enormous elongation of the body, 

 which sometimes reached a length of 75 to 80 ft. The skull is like 

 that of the Monitor among the lizards, but, according to Cope, it also 

 presents affinities with snakes. The body is snake-like, but there are 

 two well-developed pairs of limbs, forming swimming-paddles. All 

 were carnivorous and marine ; the distribution was cosmopolitan. 



Examples. Mosasaurus, Clidastes^ Liodon, Dolichosaurus. 

 Dinosauria. Terrestrial Reptiles, ranging from the Trias to the 

 Chalk, often very large, and, like Marsupials, specialised in various 

 directions. They were long-necked and long-tailed forms, some bipedal, 

 some quadrupedal. The skull has a superior and an inferior temporal 

 arcade, a fixed quadrate, teeth in sockets, and confined to the margins 

 of the jaws. They exhibit many points of resemblance to Crocodiles 

 and Rhynchocephalia on the one side and to Birds on the other. The 

 pelvis and hind -limbs are particularly avian, e.g. in the tendency to 

 form a tibio-tarsus. Brontosaurus, a gigantic, herbivorous form, nearly 

 60 ft. in length, was probably amphibious. Atlantosaurus was even 

 larger, the femur measuring over 6 ft. in length. Compsognathus, 

 Iguanodon, and Camptosaurus are examples of the "bird -footed" 

 herbivorous Dinosaurs. Compsognathw only reached a length of 2 ft. , 

 and hopped on its hind-legs like a bird. Iguanodon habitually walked 

 on its hind-limbs, and, like several others, had hollow bones ; it reached 

 a height of 15 ft. Of the carnivorous Dinosaurs, Mcgalosaurus is a 

 good type. The limbs were furnished with powerful claws, and the 

 teeth show much specialisation. 



Pterosauria or Pterodactyls. Flying Reptiles, represented from the 

 Lower Jurassic to the Upper Chalk, exhibiting many points of resem- 

 blance to Carinate Birds, but still distinctly Reptilian in type. They 

 resemble birds especially in some features of the skull and pectoral 

 girdle, but they differ markedly in. their vertebral column, pelvis, and 

 organ of flight. An expansion of the skin seems to have been stretched 

 on the much-elongated outermost finger, and to have extended back- 

 wards to the hind-legs and the tail. The long bones are hollow. The 

 sternum is keeled, and teeth are often present on the margin of both 

 jaws. There is both a superior and an inferior temporal arcade. The 

 quadrate is fixed. Some were no larger than sparrows, but others 

 the giants with which the race ended had in some cases a spread of 

 wing of nearly 20 ft. It is probable that the resemblances of these 

 forms to Birds indicate similar habits, and not any close true affinity. 



Examples. Pterodactylus^ Rhamphorhynchus % Pteranodon. 



