372 Annals of the Carnegie Museum. 



the column become gradually broader and broader ; the neural spines 

 disappear completely; the very short pleurapophyses are extremely 

 delicate, while the passages for arteries, both ventrally and laterally, 

 are much as we find them in the Petrels generally. 



All seven of the dorsal vertebra: support oblong neural spines, while 

 the haemal ones, although present in every case, are best developed in 

 the middle of the series. There is an absence of all ossification of 

 any of the tendons of the muscles of the back, so often seen in other 

 groups of birds ; while the metapophyses of the broad and well- 

 developed transverse processes are fairly in evidence. • 



The neural canal varies but little in capacity throughout the verte- 

 brae of the cervical and dorsal regions of the spine ; and upon the 

 whole, all the parts of these bones are reduced to the simplest form 

 known to occur in the vertebrse of birds. 



All the ribs are very thin and slender, with the " epipleural ap- 

 pendages " in the mid-series very long. These last are all coossified 

 with their respective ribs in the dorsal ribs, while they are entirely 

 absent in the case of the cervical and pelvic ones. Costal ribs are 

 also delicately fashioned, and the last pair of them, in either instance, 

 do not reach the costal border of the sternum, but run, in both cases, 

 into the rib next beyond, to fuse with it at a point some little distance 

 above its sternal articulation. 



Coming to the peh'is, I find it to possess characters corresponding 

 with those as they occur in the pelves of typical petrels generally. 

 That portion of it recognized as the " sacrum," made up, as it is, of 

 eleven vertebrae, is not large at its extremities, while it presents an 

 unusual swell for its middle third. Here the various outstanding 

 processes are very short and inconspicuous, although the leading two 

 of them abut against the nether surface of the ilium upon either side. 

 This also applies to the three " presacral " vertebrae, wherein the 

 diapophyses are short and connected by bone at their outer extremi- 

 ties. The last five sacrals possess much longer diapophyses, and they, 

 too, have their outer terminations fused together by an osseous con- 

 necting band, which may or may not be extended to the ultimate 

 vertebra. Upon the outer edge of this band, on either side, the sur- 

 face is molded to receive in articulation the ilium of that side, as are 

 the transverse processes of all the vertebrae beyond. 



The ossa innominata do not coosify with the sacrum, and may be 



