408 MR. Av. p. PTCRAFT OX THE [INTar. 21, 



b. Size larger, not less than 2^ in. (Bulweria alone excepted) ; postacetabular 

 iliuiu with dorsal border well-defined and terminating in a well-marked 

 spine. 

 c'. Pre-ilium moderately broad and expanded distally, resting upon the 

 synsacrum and partly concealing it; ischium having its free end more 

 or less sharply deflected. 

 e". Post-ilium with flattened dorsal aspect, rapidly tapering to form a 

 laterally-compressed blade-like edge, termmating in a spine; obtu- 

 rator foramen an elongated oval twice length of the acetabulum ; 

 free end of ischium bent at right angles to long axis, narrow and 



tapering to a point Pitffinus. 



Majaqueus. 



/". Post-iliimi i^lightly or not at all compressed dorsally ; pubis projecting 

 distinctly beyond the ischium ; ischium with broad flattened loot 

 closely articulating with pubis, 

 c'. Ischiadic foramen nearly circular; dorsal border of pre-ilium 

 concave. 

 c*. Width of dorsal aspect of post-ilium rapidly decreasing from 

 before backwards ; post-iliac spine ill-defined ... Thalassmca. 

 d*. Width of dorsal asjject of post-ilium broad throughout ; post- 

 iliac spine well-defined Priocella. 



d'. Ischiadic foramen oval ; dorsal border of pre-ilium straight. 

 e}. Thoracic vertebra immediately in front of pre-ilium fused vrith 

 synsacrum. 



a'. Entire length of pelvis not less than 3:^ in Fulmarus. 



i'. Entire length of pelvis not exceeding 2^ in Daption. 



e'. Lumbar enlargement forming a distinct tumid swelling in front 

 of acetabulum. 

 /'. Ischium never completely fused with pubis posteriorly. 



c^. Anterior border of pre-ilium obliquely truncated ; ischium 



tapering to a fine point (Eatrelata, 



d^. Anterior border of pre-ilium squarely trmicated ; ischium of 



equal width throughout Bulweria. 



g*. Pubis completely fused posteriorly with ischium ... Prion, 

 d'. Pre-ilium reduced to narrow bars, separated one from another by the 

 whole vridth of the synsacrum ; ischium in the form of a long slender 

 spine running directly backwards Pelecanoides. 



B. Pre-ilia meeting in the mid-dorsal line above the synsacral neural crest ; 

 suture dividing innominate bones from synsacrum almost or quite ob- 

 literated. 

 a. With a more or less well-marked pectineal process ; free end of ischium 

 turning downwards in a strong curve; pubis of uniform thickness 

 throughout; cavity of pelvis not divided into anterior and posterior 



renal fossa3 Ossifraga. 



h. No pectineal process ; free end of ischium not abruptly curved ; cavity of 

 pelvis distinctly divisible into anterior and posteiior renal fossie; ribs 

 of sacral vertebrae extending across renal cavity immediately behind 

 acetabulum JJwmedea. 



E. Pectoeal Limb. 



Humerus witla a shallow coraco-humeral groove ; a triangular pectoral crest 

 not extending far down the shaft; crista inferior very small, formed for the 

 most part by the downwardly-directed tuberculuni inferius ; with a large ect- 

 epicondylar process, and a more or less deep fossa for the brachialis internus ; 

 the sub-troohanteric fossa is in no case of more tliau medium size, and never 

 subdivided into two ; the ulna is without an olecranon process ; the phalanx of 

 the pollex and the 2nd phalanx of iilc. il. are of great length. 



