1901.1 SHUFELDT — OSTEOLOGY OF THE CUCKOOS. 23 



tions of these ilia, with the processes that project from their middle 

 points. As already hinted, the ilio-neural canals are here open 

 grooves, and the neural crest of the sacrum stands between them as 

 a lofty dividing wall, with much thickened superior border. This 

 latter is distinctly marked for the entire length of the sacrum, 

 otherwise the individualization of the vertebrae composing this part 

 of the bone is not very distinct, as few foramina are to be found 

 between their cfiapophyses until we reach the last one, where regu- 

 larly occurs a large pair, throwing the ultimate urosacral into bold 

 relief. 



Upon the lateral aspect of this pelvis, we not only gain a better 

 view of the largely developed propubis and the strangely formed 

 hinder portion of the ilium, but we are also enabled to get a glimpse 

 of the rather small subcircular ischiac foramen, with the reniform 

 antitrochanter in front of it. This latter faces almost directly for- 

 ward and only slightly downward, and less so outward. Beyond 

 this again is the acetabulum, with the circular perforation at its 

 base, the postero-superior arc of which merges with the periphery 

 of the outer cotyloid ring at the base of the antitrochanter, while 

 directly opposite this point the arces of these two circles are far 

 apart, and an excavation occupies the intervening space. This 

 grows less, of course, as we proceed either way toward the base of 

 the antitrochanter, where, as I have said, the inner and outer rings 

 are tangent to each other. 



The elliptical obturator foramen occupies its usual position, and 

 so close together are the postpubis and ischium that an exceedingly 

 narrow strait leads from this vacuity into the obturator space, a 

 long narrow interval between the last two mentioned bones. At 

 the centre of the triangular area among these three apertures at the 

 side of this pelvis, is found a group of small pnuematic foramina 

 which assist in admitting the air into the substance of this light and 

 thoroughly aerated bone. 



The Caudal Vertebroe and Pygostyle. — As already stated above, 

 the caudal vertebras are five in number (Plate I, Fig. 4). They are 

 chiefly noted for their high and prominent neural spines, the two 

 loftiest being seen in the third and fourth vertebrae. The diapo- 

 physes grow longer and more spreading as we proceed in the direction 

 of the pygostle, the last segment possessing them longer than any 

 of the others. We find in the third caudal vertebra a small anchy- 

 losed chevron bone, which slightly overlaps the bone in front of it. 



