Structure of the Fossil Saurians. 345 



The animal measured 7 ft. From the atlas to the tail were 

 reckoned 52 vertebrae. A portion of the head, a scapula, and 

 a fore paddle have been found ; but none of the teeth. The 

 length of the vertebrae is three fifths of its breadth. The 

 paddle is very large, and, with the humerus, occupied one 

 fifth of the length of the whole animal. The bones of the 

 paddle are almost circular : characters which neither the 

 I. communis, I. tenuirostris, nor I. intermedius, possesses. 



2. Plesiosau'rus Conybeare. 



In this animal the extreme length of the neck must surprise 

 us more than any other part of the structure : it is composed of 

 upwards of 30 vertebrae; a number far surpassing any cervical 

 vertebrae yet known, even among birds. In the structure of its 

 single parts this animal is somewhat nearer to the Saurians 

 than the foregoing. From what is known of the head, it re- 

 sembles that of the Lacertae, with characters of the Ichthyo- 

 saurus and Crocodile. The beak is of moderate length ; the 

 nasal orifices are situated, probably, as in the Ichthyosaurus ; 

 the teeth are placed in distinct alveoli ; they are also hollow 

 below, and, like the Crocodile's, contain within themselves the 

 replacing teeth. Among the teeth of the lower jaw the fore- 

 teeth, among those of the upper jaw the hind teeth, are 

 stronger and longer than the rest. Twenty-seven alveoli have 

 been reckoned on each side of the lower jaw. The general form 

 of the teeth is long, pointed, somewhat bent, and grooved 

 longitudinally. The teeth are probably different in the dif- 

 ferent species : no satisfactory decisions, however, have yet 

 been established, as regards this point. The vertebrae resemble 

 those of other Saurians more than do those of the Ichthyosau- 

 rus. They are longer, and the surfaces are both slightly con- 

 cave, and in the middle again a little convex. Many of the 

 vertebrae possess two oval pits, or fossae, on their lower side; 

 but the whole are not, as was first supposed, distinguished by 

 this peculiarity. The form of the vertebrae somewhat ap- 

 proaches that of the Teleosaurus and Metriorhynchus. About 

 90 vertebrae have been reckoned in the whole, of which 23 

 belong to the tail, and about 35 to the neck. The insertion 

 of the ribs was effected nearly as in the Crocodiles. The 

 neck measured 5, the trunk probably 4, and the tail 3, times 

 the length of the head. The opposite ribs were probably, 

 like those of the Cameleon and Anolis, united by means of 

 abdominal ribs. The sternum is formed differently from that 

 of Saurians, and even of the Ichthyosaurus. The pelvis is 

 more plainly developed than in the foregoing animal, and in 

 part resembles, in a slight degree, that of the Land Tortoise, 



