The Nothosauria were much smaller reptiles than the plesiosaurs, none of them perhaps exceeding the size of the smallest known plesiosaurs. They were semiaquatic in habit, with many curious resemblances to other semiaquatic reptiles of a later time known, as the dolichosaurs. The neck is more or less elongated, having about twenty vertebrae in the longest-necked forms; the body is moderately long, and broad, and the tail is relatively short. The vertebrae and ribs are quite like those of the plesiosaurs, that is, the vertebrae are gently concave at each end, and the dorsal ribs are attached by a single head to the transverse process high up on the arch; the cervical ribs are double-headed, precisely like those of the older plesiosaurs, one of the characters which insistently proves the relationships of the two groups. The bones of the shoulders (Fig. 46) also have many resemblances to the extraordinary ones of the plesiosaurs, though they are much less specialized. There was no sternum; the coracoids are large, though very much smaller than those of the plesiosaurs. The collar-bones are large and strong, joining each other in front of the coracoids and firmly united with the shoulder-blades at the outer extremity. Four vertebrae are united to form a sacrum, and their union with the hip bones (Fig. 47) was much firmer than was the case with the plesiosaurs. The limbs are elongated, but it will be observed in the figures (Fig. 48) that the radius and ulna, tibia and fibula, that is, the bones of the forearm and of the leg proper, are relatively very short as compared with the humerus and femur, a sure indication of the beginning of aquatic habits. The toes and fingers were doubtless webbed, and there was no increase in the numbers of bones in the digits, so conspicuous in the plesiosaurs. The external nostrils are large, but are not situated so far back near the eyes as in the plesiosaurs. There is a large pineal opening in the top of the skull, as in the plesiosaurs, but no sclerotic or bony plates have been observed in the eyes. They had ventral ribs like those of the plesiosaurs. [Illustration: FIG. 48.—Legs of _Lariosaurus balsami_, an Upper Triassic nothosaur: _h_, humerus; _r_, radius; _u_, ulna; _i_, intermedium; _ue_, ulnare; _f_, femur; _fi_, fibula; _t_, tibia; _a_, astragalus; _c_, calcaneum. (After Abel.)] No impressions of scales or bony plates have ever been found with the remains of the nothosaurs, and it is the belief that the skin was bare. A good idea of their general appearance will be gained from the accompanying restoration adapted from that of Professor Fraas (Fig. 44) and the restoration of the less highly specialized _Lariosaurus_, made from a very complete skeleton in the Frankfort museum (Fig. 49).