20 MAEINE EEPTILES OE THE OXFOED CLAY. 



oval in section; they are much constricted in the middle. The number of phalanges 

 in the several digits is unknown. 



Pelvis (text-fig. 7). — An isolated specimen of the ilium, probably belonging to this 

 genus, shows that it was very similar to that of Peloneustes described below (see p. 59). 

 The pubis (2 3U -) * s an immense plate of very thin bone ; there is a thickened portion 

 extending from the articular region to the posterior part of the median border, where 

 the symphysial surface is somewhat thickened. When the bone was uncrushed the 

 symphysial border must have been straight and extended nearly the whole length of the 

 bone. The posterior edge is thin and sharp, and is concave ; the postero-extemal angle 

 is thickened and bears two surfaces — -one, looking backwards, for union with the ischium, 

 the other forming the anterior part of the acetabulum (acet.) ; these surfaces make a 

 very obtuse angle with one another. In front of the articular surfaces the outer 

 border of the bone is concave, then it passes by a strongly convex curve on to the 

 anterior border, which is also convex and shows signs of having been fringed with 

 cartilage in life. 



The ischium (is.) is likewise a thin, greatly expanded bone, its ventral portion being 

 much elongated. In the uncrushed bone there would be a long straight median 

 symphysial surface for union with the opposite ischium ; owing to the thickening of 

 the bone opposite its neck, this symphysial surface is deepest in that region. The 

 anterior border is concave and sharp, forming the posterior edge of the obturator 

 foramen. The articular head is borne by a relatively narrow neck, in which the bone 

 is thicker than in the expanded median portion ; it bears three articular surfaces as 

 usual — one, looking forwards, for union with the pubis ; a second, looking outwards and 

 a little forwards, forming the middle part of the acetabulum ; and a third, the hind- 

 most, looking upwards and backwards, for union with the ilium (il.f.). The pelvis 

 seems to have been closely similar to that of Peloneustes described below (p. 59). In the 

 specimen here figured both the pubes and ischium have been completely flattened by 

 pressure : in their natural condition they must have been gently convex below and 

 concave above. 



Hind Limb (text-fig. 6, A). — The hind paddle is very similar to the fore, and is also 

 much the same as the hind paddle of Peloneustes described and figured below (p. 59, 

 text-fig. 23, B). It is, however, larger than the fore limb, and the femur is perhaps 

 rather less expanded distally, while the tibia and fibula are rather more elongated than 

 the radius and ulna, which they otherwise resemble. The proximal row of tarsals 

 (tibiale, intermedium, and fibulare) are much like the corresponding bones in 

 the fore paddle, and the same may be said of the rest of the tarsals, metatarsals, 

 and phalanges. 



