654 PROF. H. G. SEELET ON [A-Ug. I9OO, 



and measures 2| inches in length in a straight line; this pre- 

 acetabular part of the bone is 1| inches deep in the middle length of 

 the ilium. Posteriorly, the expanded blade of the ilium terminates 

 in a relatively small wedge-shaped post- acetabular portion rounded 

 at. the posterior extremity, which is less than 1 inch deep and more 

 than | inch long, defined by an inferior notch : this separates it 

 from the ischiac process which gives attachment to the ischium, 

 and extends equally far back. Hence this post-acetabular process, 

 though similar in form to the posterior process of the ilium in 

 Cynognathus, is not closely comparable with it on account of its 

 small size ; and because the inferior process, which here stretches 

 from the acetabular part of the ilium to the ischium, has no existence 

 in Cynognathus. This ischiac process constitutes the distinctive 

 feature of the ilium in the genus now described. 



The width of the inferior acetabular surface of the ilium is 

 1| inches. The anterior part is the acetabular articulation, flat 

 below, and at right angles to the expanded blade of the bone ; it is 

 convex externally from front to back, with the convexity produced 

 upward and forward on the anteroinferior border of the bone, 

 decreasing in amount as it extends forward. Within the aceta- 

 bulum, internal to this superior ovate acetabular surface, and 

 separated from it by a slight groove, is an oblique area towards the 

 back of the acetabulum, which extends obliquely downward and 

 inward, and may be a part of the pubic bone ; its anterior edge is 

 rounded. 



Behind this convex external acetabular surface of the ilium is 

 its flattened compressed ischiac process, extending backward and 

 slightly downward for ± inch, fully | inch deep, and terminating 

 apparently in a nearly square truncated posterior articular surface 

 for the ischium, which is slightly displaced downward. The inferior 

 surface of this ischiac process of the ilium is not articular, though it 

 formed part of the acetabulum. 



Only a small portion of the ischium is exposed; it extends 

 behind the ilium as in other Thecodonts. Its anterior articular 

 part is expanded to a large surface which forms the posterior portion 

 of the acetabulum, margined externally by a sharp edge, extending 

 convexly from above downward, measuring g inch as it is partly 

 exposed. The thickness of its superior surface for cartilaginous 

 union with the other pelvic bones appears to be § inch ; whence 

 it may be inferred that the bone is in contact with the pubis. The 

 state of preservation of the specimen affords no evidence as to 

 whether the acetabulum was perforate or imperforate ; but if per- 

 forate, the perforation must have been small, as in Cynognathus. 



Behind the articular surfaces of the ischium the bone is com- 

 pressed to a sharp superior external edge, and is preserved for only 

 lg inches of its length. The superior border is gently concave, and 

 the inferior external surface is deeply concave behind the articu- 

 lation, and is then flattened. So far as preserved, this condition 

 of the ischium is essentially similar to that in Cynognathus, 

 and unlike any other animal, though with some approximation to 

 Microgomphodon. 



