OPHTHALMOS A URUS. 



59 



of the bone, including the upper part of the trochanteric ridge, is covered by coarse 

 rugosities, showing that there was an external cap of cartilage. From the head the 

 shaft narrows rapidly, at the same time becoming compressed dorso-ventrally towards 

 the distal expansion, which is relatively smaller than in the humerus. Distally the 

 femur articulates with two bones only, the tibia (f.) and fibula (/!), the facets for which 

 are shown in text-fig. 41, D (t.f. & f-f.). It will be seen in the specimen figured 



Text-fig. 40. 



acet. 



Left ischio-pubis of Ojpliihalmosaurus (f nat. size) : A, from outer side ; B, proximal end ; C, from inner side. 



acet,, acetabulum ; il.f., facet for ilium ; isch., ischium ; oh.f., obturator foramen; pu., pubis; 



v.h., ventral border. 



that the smaller of these two bones is the tibia and that it is irregularly oval in outline, 

 articulating proximally with the femur, distally with the tibiale and intermedium, and 

 postaxially with the fibula. 



In some other specimens the ossification of the anterior edge of the tibia is more 

 extensive, so that the anterior border is sharp and slightly concave, and the whole bone 

 as large as or larger than the fibula. This latter is roughly pentangular in shape ; it 



l2 



