THEUUMOUPns. 457 



\isi'(l as an article of food l)y tlio natives, ami suft'eiinfj fniin tlie introiliietion of hogs, 

 they have become inicominnii, aiul will soon be niuubered with tlie animals wiiich once 

 existed but are now extinct. 



Of the fossil members of this order, the Proterosaurus is of particular interest, as 

 it was the first known fossil rei)tile, being described as early as 1710 from fragments 

 obtained in the ]iermian beds of Thuringia. A study of the bones of the head, neck, 

 and liml)s shows it to have been an a(jnatie animal of considerable size, capable of seiz- 

 ing and retaining the active lislies which sported in the waters that deposited the old 

 Thuringian cojiper-slates. lihijnchosaurus, from the trias of England, is of interest in 

 that the jaws, like those of turtles, are unprovided with teeth, and the prcmaxiilaries 

 present a curved beak, strongly resembling that of birds. The vertebral centra are, 

 however, like those of JIattcrIa, i)iconca\e. ILjperodapedon^ also triassic, is au allied 

 form. 



Order VI. — ICHTli YOPTER YGIA. 



The members of this order arc all extinct, and are only known from their fossil 

 remains, which have been found in the tertiary deposits of the Old World. Though 

 true reptiles in structure, the Ichthyosauri resembled in general outline, antl jirobably 

 also in habits, the cetaceous mannnals of to-day. The broad head, short neck, thick 

 body and short vertebrre resemble these ])ortions of the whales, a general resemblance 

 carried still further by the flip]>er-like limbs and elongate, probably tin-be.nriiig, tail 

 which jierformed the office of a iiro]>eller. Some of these saurians were colossal in 

 size, reaching a length of forty feet, though many were smaller and resembled the dol- 

 jihins, being about six feet or even less in length. That the animals were rejitiles is at 

 once seen, however, on an examination of the bniiii cavity, which is of most diminu- 

 tive size when compared with that of sea-mammals, and is not protected by a solid 

 cranium, the bones of the head being more or less imperfectly united together. The 

 vertebral centra, moreover, were biconcave, and the orbits, which were enormous, some- 

 times fifteen inches in diameter, were protected by a circular series of triangular i)hites 

 ■which may have assisted in adjusting the focus of the eyes, or may have been in their 

 nature merely protective. A study of the jaws, as well as of the half-digested contents 

 of tlie alimentary tract, proves the Ichthyosaurus to have been a predatory animal, in- 

 habiting the open sea as well as the shores, and feeding on fish and other marine 

 animals. Though awkward in its movements, it not infrequently quitted the water 

 and crawled out on some ex])osed sand-bar to rest or to bask in the sun. I. commimis 

 is the most common form. 



The Sauranoclo7i, found in the Jurassic deposits of the west, resembled the Ichthyo- 

 saurus very closely, though it differed in being destitute of teeth. It is given by some 

 an ordinal, while others consider it of only family, value. 



Order VII. — THEROMORPHA. 



This order includes several extinct reptiles, fragments of which are found chiefly in 

 the Permian and triassic fresh-water dejiosits of South Africa. The teeth are either 

 wanting or are represented by a jiair of maxillary teeth. The vertebrre arc biconcave, 

 and the amliulal'uy liml)s are su]iported by a solid pelvis and firm shoulder-girdle. It 

 was from this order that the mammals are by some supposed to have branched off. 



