1899.] OSTEOLOGY OF THE TUBIKABES. 407 



b'. Posterior border of sternum with four deep notches ; spina externa 



blunt or bifid Puffi7ius. 



Maj'cujweus. 

 Bulweria, 

 Prion. 

 (Estrelata. 

 Payodroma. 

 c'. Outer pair of notches obliterated or feebly developed (sometimes forming 



fenestra) Priocella. 



Thalassceca. 

 Fulmarus. 

 Priofinus. 

 d'. Posterior border of sternum with 4 yery slight notches ; corpus sterni 

 with pneumatic opening on anterior region of dorsal surface. 



Ossifraffa. 

 b. Coracoid grooves forming a right angle with the sternum ; base of coracoids 

 not more than \ the width of the long axis ; sternal ribs almost en- 

 tirely confined to anterior lateral process ; furculum without a distinct 

 hypocleideum ; posterior border of corpus sterni entire... Pelecanoides. 



B. Pneumatic foramina of dorsal surface of sternum conspicuous, extending 

 along the whole length of median line of the sternum ; carina merging 

 into the sternal plate some distance in trout of the metasternum ; posterior 

 lateral processes projecting far beyond the level of the metasternum. 



BiomedeidtB. 



D. Pelvic Giudle. 



Pre- longer than post-acetabular ilium ; ischium produced far backvfards in 

 the form of a long narrow bar of bone, its free end deflected and firmly bound 

 to, or even fused with, the pubis, so that the obturator fissure is closed 

 behind ; obturator foramen never completely shut off from the fissure. 



A. Pre-ilia not meeting in the mid-dorsal line above the neural crest of the 

 synsacrum ; innominate free. 



a. Size small, total length of pelvis not exceeding 1-4 in. ; postacetabular 

 ilium with its dorsal border obliquely truncated and ill-defined ; free 

 ends of ischium and pubis fused. 



a'. Obturator fissure very narrow ; pre-ilia widely separated ; obturator 

 ioramen open posteriorly; lumbar enlargement of synsacrum large 

 and lying in front of the acetabular region. 



a". Pre-ilium not expanded distally ProccUaria. 



b". Pre-ilium expanded distally Oceanodroma . 



b'. Obturator fissure very wide ; lumbar enlargement of synsacrum sUght, 



lying iu mid-acetabular region. 



c". Pre-ilia not rising beyond the level of the base of the synsacral 



neural crest ; obturator foramen separated from the fissure by a 



broad bar of bone Pelagodroma. 



d". Pre-ilia rising to the level of the top of the neural crest, or 

 nearl}' so. 



a^. Obturator foramen and fissure confluent. 



a*. Dorsal border of pre-ilium pressed closely to the lumbar en- 

 largement, which is almost entirely preacetabular ; greatest 

 width of .synsacrum about ^ its length Oceanites. 



6^. Dorsal border of preilium separated by a deep groove from the 

 lumbar enlargement; greatest width of synsacrum about | its 

 length Cymodroma. 



i'. Obturator foramen separated from the fissure by a broad bar of 



bone ; pre-ilia pointed in front .. Fregetta. 



27* 



