1866.] HUXLEY — SOUTH AFRICAN DINOSAUEIA. 3 



The most perfect femur of Megalosaurus BucMaiuU in the same 

 collection is 62 inches long, while the middle of the shaft is not more 

 than 4 inches in diameter. The largest Megalosanrian femur in the 

 British Museum could hardly have exceeded 33 inches in length 

 when entire. 



The femur of SceUdosaurus is much smaller. Thus while the 

 thigh-bone of the African Dinosaurian was probably nearly as long 

 as that of Megalosaurus, it was absolutely, and a fortiori relatively, 

 stouter. 



On comparing the femora of Megalosaurus and Iguanodon, I find 

 the following to be the chi^ differences between the two : — 



In Megalosaurus — 

 a. The shaft is more slender and proportionally deeper from before 



backwards. 

 h. The inner trochanter lies almost wholly in the proximal half of 

 the bone, so that its central, most projecting, part is much nearer 

 the proximal than the distal end of the bone. In Iguanodon 

 the most projecting part of the inner trochanter is a sudden 

 outgrowth from its distal end, which lies altogether in the distal 

 half of the bone. 



c. One face of the inner trochanter continues the direction of the 



tibial (or inner) face of the femur. In Iguanodon one face of 

 the inner trochanter looks towards the dorsal side of the 

 femur, or is at right angles with the tibial face of the shaft, 

 and there is a fossa above the trochanter on the tibial face of 

 the femur. 



d. The proximal end of the femur is curved, flattened, and twisted 



on its axis, so that the long axis of its transverse section makes 

 an acute angle with that of the shaft of the bone. In Iguano- 

 don the proximal end is flattened, but almost straight and not 

 twisted on its axis, whence the long axis of its transverse 

 section coincides, or nearly so, with that of the shaft of the 

 bone. 



e. The concavity of the upper face and convexity of the lower face 



of the proximal part of the femur is strongly marked. In 



Iguanodon both faces are almost flat. 

 /. The inner contour of the proximal part of the femur makes a slow 



and gradual curve. In Iguanodon it makes a sharp, almost 



rectangular, bend. 

 g. The great trochanter is comparatively short, not nearly reaching 



the proximal end of the bone. In Iguanodon it is long, slender, 



and its summit attains the level of the proximal end. 

 h. There is but a shallow and wide excavation on the front face of 



the distal end of the femur. In Iguanodon there is a deep, 



sharply defined longitudinal furrow on this face, nearer the 



outer than the inner condyle. 

 i. The isthmus uniting the inner and outer condyles is wide from 



before backwards. In Iguanodon it is very narrow. 

 h. The outer condyle has a peculiar posterior ridge-like process, 



which appears to be absent in Iguanodon. 



B 2 



