66 



BULLETIN 110, UNITED STATES NATIONAL MUSEUM. 



mm., its maximum thickness. The truncated anterior end of the blade presents a 

 thin, sharp edge. The anterior portion of this blade particularly the lower border, 

 from where it joins the peduncle flares outward, at an angle of nearly 45° from the 

 main axis of the bone (see fig. 1, pi. 10), but the posterior extremities are parallel, 

 while in the middle, especially superiorly, the ilia of opposite sides closely approach 

 each other along the upper median border, being very bird-like in this respect. 

 Viewed laterally when articulated with the sacrum, the superior borders of the ilia 

 extend above the tops of the spinous processes of the three anterior sacrals, as 

 shown in plate 8, whereas in Ceratosaurus the opposite condition prevails. 



On both the inner and outer surfaces and at right angles to the superior border 

 are prominent striations evidently for the better insertion of the muscles which 

 attach there. 



Measurements of Ilia of Antrodemus valens. No. 4734, U.S.N. M. 



Left. 



Eight. 



Greatest length 



Height above middle of acetabulum 



Height above pubic peduncle 



Length of acetabulum 



Length of pubic articulation 



Width of ischiac articulation 



mm. 



mm. 



672 



720 



283 



335 



392 





180 



222 



177 





78 





Pubis (p.). — In specimen No. 4734, U.S.N.M., both pubes are present although 

 their form has been somewhat altered by transverse crushing. Fortunately others 

 in the collection enable me to determine the amount of this distortion. 



In Antrodemus the pubis is relatively long, with a heavy expanded proximal 

 end and an elongate, triangular, massive foot-like distal end. The articular sur- 

 face for the iliac peduncle is rugosely roughened, and shallowly concave antero- 

 posteriorly, and articulates closely with the peduncle. In aged individuals it 

 would no doubt become coossified with the ilium, as it has in the type of Cera- 

 tosaurus nasicornis, (pi. 23), and as is occasionally found in members of the Sauro- 

 poda. Posterior to the iliac articulating surface this end presents a short beveled 

 surface that looks upward and backward, forming the pubic contribution to the 

 boundary of the acetabulum. Posterior to this surface a vertical face, with rough- 

 ened surface, articulates with an anterior branch from the ischium, thus completing 

 the lower boundary of the acetabulum. There is no true pubic foramen, though 

 a notch on the inferior side below the acetabular portion, probably functions in 

 that capacity. Below the proximal end the shaft of the pubis rapidly diminishes 

 in size, the greatest diameter changing from an antero-posterior direction to a 

 transverse one. The shaft is very thin and sharp along its internal margin but 

 much thickened and rounded externally, very similar in this respect to the pubes 

 in the Sauropoda. 



The distal end expands into an elongate, triangular foot, pointed behind and 

 wide in front, or shown in figure 47, B.; the greatest extension being in a posterior 

 direction, whereas in Tyrannosaurus this condition is reversed. The inferior sur- 

 face is flat but roughly rugose, as for the attachment of a heavy pad of cartilage. 



