n; 



CLASS REPTILIA. 



next subfamily. Machimosaurus, which occurs both in France and 

 England, is the largest member of the order, the length of the 

 mandible exceeding 50 inches ; the skull has been referred to 

 Pliosaurus. The teeth closely resemble those of Goniofiholis, 

 having conical and deeply fluted crowns. 



With the second subfamily, or Metriorhynchince, we come to a 

 very remarkable group of Crocodiles, presenting certain specialised 

 features unknown elsewhere in the entire order. The skull (fig. 

 1087) is either of moderate length or comparatively short; the 

 nasals are either in contact with the premaxillse, or separated there- 

 from by a short interval ; the nares are directed frontally ; the orbits 

 are of very irregular contour, and placed completely on the sides of 

 the skull ; and the teeth, which are never very numerous, are 

 always of considerable size, and directed more or less nearly 



Fig. 1087. — The cranium of Metriorhynchus hastijer ; from the Kimeridge Clay of Normandy. 

 One-sixth natural size, fimx, Premaxilla ; 7)ix, Maxilla ; na, Nasal ; a, Prefrontal ;_/V, Frontal ; 

 or, Orbit. (After Deslongchamps.) 



vertically, while there is no vacuity in the mandible. The most 

 remarkable features of the group are, however, the development 

 of a ring of bony plates in the sclerotic of the eye, and the 

 general or universal absence of a dermal armour. It is, indeed, 

 very curious to notice the correlation of these two features, since 

 there is no known instance of the presence of both sclerotic plates 

 and of dermal scutes in any reptile. The pelvis of this subfamily is 

 also worthy of notice. Thus the ilia are very small subtriangular 

 bones articulating with long and downwardly curved sacral ribs ; 

 while the ischia are enormously large, with the shape of an isosceles 

 triangle. This presents a remarkable contrast to Steneosaurus, where 

 the sacral ribs are straight and directed outwards, while the ilium is 

 larger, with a considerable portion projecting above the costal artic- 

 ulation. In the genus Metriorhynchus the skull (fig. 1087) is of 

 moderate length, and frequently somewhat slender, with the frontal 

 region slightly sculptured ; there is a more or less well-marked pre- 

 maxillary expansion ; the prefrontals (a) are very large, and over- 

 hang the orbits ; while the teeth are curved and carinated, with the 



