SHUFELDT : OSTEOLOGY OF THE STEGANOPODES 143 



is found. On the opposite side of the coracoidal head we find a group of pneumatic 

 foramina, and below these a peculiarly formed scapular process, a spine-like apo- 

 physis, which rather gracefully curls upward and then toward the shaft of the bone. 

 This latter portion of the bone is subcylindrical and smooth, dilating below into 

 a transverse fan-shaped sternal extremity. 



A scapula offers but a very small portion of the articular surface for the glenoid 

 cavity ; not more than an eighth of it in all the specimens examined by me. The 

 head of the bone then reaches forward and inward, but only the (juter two thirds 

 of this makes an indifferent articulation with the narrow and roughened border of 

 the scapular process of the coracoid. The shaft of the bone is quite stout behind 

 this and somewhat compressed in the vertical direction, while posteriorly it fiat- 

 tens out into a broad paddle-shaped extremity that finally tapers to a point 

 behind. 



Even more than it is in the case of the sternum, the bones of the shoulder-girdle 

 in all the species of the Sulidse at my hand are, apart from their specific variance in 

 size, almost identically alike in each and every one of their corresponding characters. 

 As for the bones of the shoulder-girdle in the Phaethonidse, we may say here, by way 

 of comparison, that it is only in the scapula where we see the characters which more 

 or less resemble the corresponding ones as we find them in the scapulae of the Sulidse. 

 Neither the os furcula nor a coracoid of a gannet or booby bear any special resem- 

 blance to those bones as they exist in the tropic Ijirds. 



Of the Pelvis and Caudal Vertehrx. — The first vertebra that anchyloses with the pelvic 

 sacrum anteriorly projects entirely beyond the iliac bones. Its centrum, in common 

 with the next three that follow it, is much compressed from side to side, and its neural 

 spine is continuous with the common neural ridge above the succeeding segments. 



The first five vertebrae that lie beneath the ilia throw out their apophyses in the 

 usual way for their support ; the last two of this series meet the iliac margins. 

 Here the neural canal and centra are large, in order to afford room for the increase 

 in size of the cord where the sacral plexus is thrown off. 



The twenty-eighth and twenty-ninth vertebrae have their processes thrown directly 

 upward, so that they are scarcely visible upon direct ventral aspect. 



In the thirtieth vertebra they are powerfully developed and extend directly 

 across the basin to abut by anchylosis against the pelvic walls immediately behind 

 the cotyloid cavity on either side. From this point the centra of the so-called uro- 

 sacral vertebrae taper quite rapidly in size to the ultimate one, which, in *S'. hassana, 

 is enlarged and exhibits a big facet on its posterior aspect, intended for the first free 

 caudal. In *S'. piscator this enlargement is not evident. 



