SHUFELDT : OSTEOLOGY OF THE STEGANOPODES 



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Upon lateral view of this pelvis we note that the ischium (upon either side) is 

 much drawn out behind, and there pointed. It may be said that hardly any ilio- 

 ischiadic notch exists, the usual site for it being very shallowly rounded off. For 

 their anterior moieties the pubic styles are very slender, but their elongated pos- 

 terior ends are more clubbed and thickened, where they come simply in contact 

 with either ischium above them. On the lateral aspect the antitrochanter is seen 

 to be not very prominent ; and the cotyloid ring and ischiadic foramen have their 

 usual ornithic characters. Posteriorly, the obturator foramen opens most com- 

 pletely into the space of the same name ; thus, in reahty, merging the two vacuities 

 into one. In the capacious pelvic basin on 

 the ventral aspect we had the last six parap- 

 ophysial struts of the vertebrae, when pres- 

 ent, very distinct and slender, being thrown 

 up as braces in the usual manner. This fea- 

 ture also obtains with all the vertebrae at the 

 fore part of the sacrum, and indeed, there are 

 only two in the series that entirely lack this 

 development of the parapophysial processes, 

 they being the twenty-sixth and twenty- 

 seventh of the vertebral chain as a whole. 



This pelvis is very light and highly pneu- 

 matic; air-holes always occurring in a small 

 group immediately in front of either cotyloid 

 ring, as well as in many other places. 



Moreover, in many respects the pelvis in 

 Fregata is a very differently characterized 

 bone from what we find in an Albatross. 



In the skeleton before me, I find six large, 

 free caudal vertebrse, besides a big parallelo- 

 grammatic pygostyle. The vertebrae have 

 very long, depressed, narrow diapophyses, 

 the anterior and posterior borders of which are rounded off. Stumpy, bifid, 

 centrally perforated haemal spines are found only in the last two or three, while in 

 all these vertebrae, so light from the high state of pneumaticity they enjoy, the 

 neural spines are elevated and pointed. The neural canal, nowhere very large, 

 seems to extend even into the pygostyle. This latter bone has a rounded superior 

 border, while below and behind it is thickened and broadened. At its lower part 



Fig. 37. Dorsal aspect of the pelvis of Fregata 

 aqidla, very slightly reduced. From a photograph 

 by the author of the specimen in the collection of 

 the U. S. National Museum (No. 18485). 



