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, scapule, clavicles, and a T-shaped episternum, 
but there is no sternum. The skull has a long tapering rostrum, large 
orbits, « large parietal foramen, and usually sharp conical teeth in a 
continuous groove. The vertebree are deeply amphiccelous. There 
was no dermal armour. The length of the body is sometimes 30 to 
40 ft. Some species were viviparous. 
Examples.— Jchthyosaurus, 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.—Aosasaurus, 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, eg. in the tendency to 
form a tibio-tarsus. Arontosaurus, a gigantic, herbivorous form, nearly 
60 ft. in length, was probably amphibious. A¢/antosaurus was even 
larger, the femur measuring over 6 ft. in length. Compsoguathus, 
Iguanodon, and Camptosaurus are examples of the ‘‘bird-footed” 
herbivorous Dinosaurs. Compsognathus only reached a length of 2 ft., 
and hopped on its hind-legs like a bird. Jguwanodon habitually walked 
on its hind-limbs, and, like several others, had hollow bones ; it reached 
a height of 15 ft. Of the carnivorous Dinosaurs, Megalosaurus is a 
good type. The limbs were furnished with powerful claws, and the 
teeth show much specialisation. 
Pterosauria ox Pterodactyls,—F lying 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.—Prerodactylus, Rhaniphorhynchus, Pteranodon, 
