374 Annals of the Carnegie Museum. 



those bones of the skeleton of the tail. No pygostylc at all occurs 

 among the material, which is somewhat remarkable, for an unusual 

 number of cervical and dorsal vertebrae were found, and the terminal 

 piece of the tail is comparatively large in all petrels. The caudal 

 vertebrae are of simple form in mid-series, with short, rather stout 

 diapophyses that are bent downwards. Neural spines are also present 

 in the majority of them, while apparently the last segment or two 

 possessed a bifurcated haemal spine. It would appear as though the 

 neural canal extended posteriorly as far as the pygostyle, for it is 

 present in all these caudals in the collection. 



In all probability ^. vociferans possessed seven (7) caudal verte- 

 brae and a pygostyle. The tubinarine form possessing the greatest 

 number of these caudal vertebrae is Pelecanoides urinatrix, which has 

 nine (9) and a terminal piece. Forbes, in his above-cited table, gives 

 nine, but does not count the pygostyle (fig. 21, PI. XX). This is a 

 mistake, I think, unless it be generally understood that the aforesaid 

 terminal bone is, in a way, to be reckoned as an ossification apart 

 from the vertebral chain as a whole. 



The Stermnn and Shoulder Girdle. — As will be noted from the lists 

 given above, there are nearly a dozen sterna of the petrel here being 

 examined in the collections at hand, and plenty of scapulae, coracoids, 

 and OS furcuhe to study and compare, with the view of noting the 

 characters of that part of the skeleton. (See figures of these several 

 bones on Pis. XXII, XXIII, XXIV, and XXV.) 



The sternum varies to some extent in some individuals, but prob- 

 ably not for sex. In some the outline of the body is nearly square, 

 while in others it is more, or slightly more, parallelogrammatic. 

 There is also a variance in the widths and lengths of the xiphoidal 

 processes, they being short and narrow in some sterna, and rather 

 wider and longer in others. The bone appears to always be non- 

 pneumatic, and when viewed from above the body presents a great 

 concavity with respect to form. The triangular and pointed costal 

 processes flare out, one upon either side, and there are, as a rule, six 

 narrow facets upon either costal border for articulation with the 

 costal ribs or haemapophyses. Its anterior border is thickened so as 

 to afford surfaces for articulation with the coracoids ; they meet each 

 other anteriorly at an angle of nearly 90 degrees, there being a well- 

 pronounced transverse notch at the apex of the angle in the mid- 



