186 



MAEINE EEPTILES OF THE OXEOED CLAT. 



The pelvis of a young individual (E. 2417) is shovrn in text-fig. 92. None of the bones 

 are completely ossified, but the immaturity of the pubis is most striking, there 

 being no trace of the antero-external angle or of the articular surfaces ; these must 

 have been still cartilaginous. The ilium is less expanded at the ends, while the 

 ischium, though resembling that of the adult more than is the case with the other 

 elements, has its articular surfaces rounded and not sharply defined. 



Hind Limb. — The femur (text-figs. 91 B, 9d,fem.) is not greatly expanded at its 

 distal end like the humerus. Its proximal end in fully ossified specimens bears a 

 convex head, oval in outline, the surface of which is roughened and was covered with 

 cartilage. The trochanter is large and prominent ; its cartilage-covered upper end is 

 continuous with that of the head ; anteriorly and posteriorly it is marked off from the 



Test-fig. 92. 



acet. 



Immature pelvis of Ci-yptocleidws oxoniensis, from above. (E. 2417, j nat. size.) 

 acet., acetabulum ; il., ilium ; isc, ischium ; olt.f., obturator foramen ; pu., pubis. 



upper part of the shaft by longitudinal grooves, of which the posterior is the more 

 strongly marked ; its outer surface is raised into ridges and roughened for muscle- 

 attachment. The shaft is oval in section and bears on its ventral face and posterior 

 border strong rugosities for muscle-attachment. The distal end, as already noted, is 

 much less expanded than is the case with the humerus ; it articulates only with the 

 tibia and fibula, the facet for the first being slightly concave, that for the latter nearly 

 flat. 



The tibia (text-figs. 91 B, 93, t.) has a slightly convex femoral border; its preaxial 

 edge is also convex ; its inner (postaxial) border for union with the fibula is sometimes 



