32 MAEIXE EEPTILES OF THE OXEOED CLAY. 



Pelvis (text-fig. 10). — This is chiefly remarkable for the large size and extreme 

 thinness of the pubes and ischia and for the great elongation of the latter. The 

 pubis (pit.) is a broad sheet of bone; its inner (symphysial) border is nearly straight 

 and is a little thickened in its posterior third. The anterior edge is broadly convex and 

 in life was fringed with cartilage. The outer border is sharp and concave. Postero- 

 externally the bone is somewhat thickened and bears two surfaces, the anterior forming 

 the front of the acetabulum, the posterior, making a very obtuse angle with it, 

 uniting with the ischium, there being, as usual in the group, no union between the 

 pubis and ilium. Internal to the surface for the ischium the posterior border is sharp 

 and concave, forming the front of the obturator foramen, which seems to have been 

 closed by a backward projection of the median portion of the pubis meeting a 

 corresponding forward projection of the ischium (is.). This latter is, in the main, 

 a greatly elongated plate of bone uniting with its fellow in the middle line in a straight 

 suture ; at its anterior end it is somewhat thickened, so that the symphysial surface is 

 there deepened. Posteriorly the bones diverge a little from one another, but in life 

 were probably united by cartilage for some distance behind the true symphysis. The 

 posterior end of the bone is rounded, the outer border concave. The prominent 

 thickened antero-external region is separated from the main body of the bone by a 

 neck ; it bears, as usual, three facets, the anterior for union with the pubis, looking 

 directly forwards, the middle one forming the middle part of the acetabulum (acet.), and 

 the posterior looking somewhat upwards and outwards for articulation with the ilium. 

 Internal to the pubic facet the anterior border of the bone is sharp and concave, 

 forming the hinder border of the obturator foramen. Internal to this, again, is the 

 median prominence for union with the pubis, the pubic-ischial symphysis being, as 

 above noted, continuous from end to end of the pelvis. 



The ilium (il.) is greatly crushed, particularly at its upper end, which seems to have 

 been somewhat expanded ; at the distal end there are the usual two facets, one for union 

 with the ischium, the other forming the posterior portion of the acetabulum (acet.). 



Hind Limb (text-fig. 9, B). — The femur is considerably longer than the humerus, but 

 is very similar in form. The trochanter (tr.) is well developed and is defined 

 posteriorly by a shallow groove, which extends some distance down the posterior face 

 of the shaft, the outer border of the lower end of the groove bearing a strong angular 

 prominence (m.r.) with rugose surfaces for the attachment of muscles ; beneath this 

 point the shaft is oval in section, though the antero-posterior diameter is not much 

 greater than the vertical one. The distal expansion is similar to that of the humerus. 

 It bears two facets for union with the tibia and fibula, and for the rest seems to have 

 been fringed with cartilage. The tibia (t.) and fibula (f.) are almost exactly similar 

 in form to the radius and ulna, though perhaps a little longer in proportion to their 

 width. Their relation to the proximal row of tarsals is the same as that existing 

 between the radius and ulna and the proximal row of carpals. 



