.310 Annals of the Carnkgie Museum. 



lateral aspect, the acetabular ring is seen to be large, nearly circular in 

 outline, with raised antero-external margin. 'I'he antitrochanter is 

 also conspicuously developed. Behind it is the very extensive open- 

 ing of the ilio-ischiac foramen, which in this species is so broadly ellip- 

 tical in outline, as to appear more than usually circular — its minor axis 

 being about three-fourths the length of the major one. Posterior to 

 this foramen the side of the pelvis is both deep and smooth, with but 

 the barest suspicion of an ilio-ischiac notch in its hinder margin. The 

 "obturator foramen" and the "obturator space" hr.ve practically 

 merged into one, there being barely an osseous isthmus dividing them. 

 The latter is very large owing to the deep downward sweep of the 

 pubic bone, and the concavity of the inferior margin of the ischium. 

 The. puh's is long, narrow and slender, being nearly of uniform width 

 throughout. It projects nearly two centimeters beyond the ischium 

 behind, and its extreme tip is slightly spatulate and decurved. 



Yentrally, we are to notice that the first sacral vertebra, though 

 considerably larger than any of the others, is still smaller than the last 

 free dorsal one, and has many of its characters, notwithstanding its 

 complete fusion with the remaining vertebrae of the sacrum and with the 

 ilia. The four that succeed it throw out their lateral processes to the 

 under surface of the ilium on either side, to completely coossify there 

 with those bones, or, as in the case of the last two of these four, to 

 press closely against them. After these there next abruptly follows 

 the deep concavity of the pelvic basin, showing, in either one of its 

 lateral walls, the very circular and smooth internal ring of the acetab- 

 ulum, and the large ischiac foramen. These are separated by a strong, 

 though narrow osseous isthmus, the upper part of which, upon either 

 side, serves as an abutment against which rest the outer expanded ex- 

 tremities of the produced parapophyses of what are really the two true 

 sacral vertebrae. The next four sacral vertebrae have their lateral pro- 

 cesses elevated, vvith their dilated outer ends abutting against the mesial 

 margins of the ilia, but in the ca.se of the last two of these no anchy- 

 losis takes place where they meet. As already explained, the ulti- 

 mate sacral vertebra projects beyond the iliac bones behind. (See 

 Plate XI II., Fig. 7.) 



Within the pelvic basin small groups of pneumatic foramina occur 

 in various places, and a strongly-marked rounded ridge passes longi- 

 tudinally over about the site of the original line of meeting of the ilium 

 and ischium of either side. The pubic bones are nowhere in con- 



