l6 Shufeldt, Osteology of OrtJwrhamphus magnirostris. r,^f"\",i. 



sacral vertebra; or " sacrum," and exhibits a d.eep " ischiadic 

 notch " on its posterior margin.* 



Viewed upon its dorsal surface, there is to be noted the parial 

 intervertebral foramina, which, beginning small at the posterior 

 apertures to the ilio-neural canals, continue so as to include the 

 fifth pair, whereupon they become very considerably larger, being 

 elliptical in outline, and maintain nearly a uniform size to the 

 ultimate pair. 



The sacrum is broadest at a point between the trochanters, and 

 narrowest at its posterior termination, the margin joining these 

 two points, on either side, being nearly a straight one. This line 

 or sacral margin is likewise in close contact with the opposing 

 border of the ilium, and it is very probable that in old individuals 

 these two elements of the pelvis may anchylose along these 

 borders ; they appear to be nearly in that condition in the 

 specimen at hand. 



The post-acetabular part of either ihum. on this view of the 

 pelvis, is convex throughout its extent for the anterior three- 

 fourths of its area, while the hinder fourth is decidedly concave, 

 which concavity is limited behind by the free margin of the ilium, 

 and at the side by the conspicuously raised and sharp border of 

 the same pelvic element. This latter border forms the internal 

 edge of an ilium, as far back as a point opposite the cotyloid 

 cavity, after which it forms the raised bounding crest standing 

 between the post-acetabular area and the side of the pelvis. 



On its ventral aspect we have to observe the capacious pelvic 

 basin of this bone, and the not very strong pair of transverse 

 processes of the eleventh sacral vertebra, which are carried far 

 out, transversely, as braces to points slightly posterior to the 

 antitrochanters. Beyond this, the united centra of the sacral 

 vertebra? exhibits, as usual, considerable enlargement in order to 

 accommodate the increased size of the spinal cord in this part 

 of its continuity. In the present instance, this enlargement is 

 somewhat above the average for a bird of this size ; it is hidden 

 by the sternum in fig. 8 of Plate V. 



The ventral surfaces of the ilia are flat and smooth throughout 

 their entire extent, and the two pairs of sacral ribs, where they 

 come in contact with these surfaces, completely anchylose there- 

 with throughout the entire fine of meeting. The fourth, fifth, 

 and sixth sacral vertebrae have their transverse processes extended 

 laterally as braces to the ventral surfaces of the ilia opposite 

 them, and it is at this point that the pelvis of Orthorhamphiis is 

 narrowest transversely. 



As already stated above, the skeleton of the tail m this bird 

 consists of seven vertebrae and the pygostylc. This latter has a 



♦Doctor Gadow, in describing "the Pelvic Arch" in the article 

 " Skeleton " in Newton's " Dictionary of Birds," letters this notch inc. 

 isch. ; but nowhere states what those letters stand for. This likewise applies 

 to the letters Inc. isch. pub. for the obturator space (obturator vacuity or 

 obturator interspace of Owen) in the same work. 



