1899.] OSTEOLOGY OP THE TUBIlifAEES. 397 



(PI. XXIII. figs. 3, 4). This last differs from that of the Impennes, 

 which I described recently (16), in that it is almost quadrate 

 instead of triangular. It is notched at each end. The outer limb 

 o£ the anterior notch fits into yet another notch formed between 

 the inturned dorsal crest of the palatine and the outer border 

 of the posterior end of the vomer. The posterior notch forms an 

 articular surface for the pterygoid. The palatine runs backward 

 to the pterygoid so as to completely conceal the hemipterygoid 

 from below. 



The dentartj, aaf/ular, supra-angulm% splenial, and coronokl are 

 all still traceable, but fusion of these elements has begun. 



iv. The Veetbbbal Column. 



All the presynsacral vertebi'ae are free, the thoracic are 

 heterocoelous. The cervicals somewhat recall those of the Stegano- 

 podes. The odontoid ligament of the atlas is not ossified. The 

 neural arch is deeply notched anteriorly and posteriorly, and meta- 

 and hyperapophyses are more or less well developed. In many 

 the anterior cervicals have a bony bar running forward from the 

 hyperapophysis to the base of the anterior zygapophysis. Neural 

 spines are well developed from the 2ud to the 5th vertebrse. 



The hyperapophyses of Diomedea are less well developed than 

 in the Procellariidse. 



The thoracic vertebrae in the Procellariidae bear hypapophyses ; 

 these are absent in the Diomedeidge. The anterior hypapophyses 

 terminate anteriorly in a flattened plate. Below the neural canal 

 the centra of the vertebrae bear each a deep depression, Avhich in 

 some — e. g., Osslfraga, Dioniedea — becomes a large aperture into 

 which open numerous pneumatic foramina. Similarly, in Ossi- 

 fraga, Dioniedea, and the larger Petrels there are large pneumatic 

 apertures opening above the neural canal and below the transverse 

 processes. The vertebrae of sections A and B of the Procellariidae 

 are non-pneumatic. 



The synsacrum includes some 13 vertebrae. Of these, the 8th 

 or 9th represents the first true sacral and lies behind the acetabulum. 

 Only in a feAv genera — e. g., Majaqueus, Priofinus, Diomedea — is 

 there any distinct division into anterior and posterior renal fossae. 

 In many genera, e. g. Puffinus, all traces of the original sacral 

 A^ertebrae are lost. In Pujffinus the acetabulum lies immediately 

 behind the parapophysis of the last lumbar vertebra ; in no other 

 genus do these relations exist, though the one is never far removed 

 from the other. 



There are 8 postsynsacral vertebrae (free caudals) including the 

 pygostyle. The intercentra of these vertebrae have been described 

 and figured by Beddard (2). There are 15 cervicals, of which 

 the last 3 or 4 bear free ribs increasing in size from before 

 backwards. The thoracic vertebrae are 7 in number : making a 

 total of 43 in all. In FuJmarus and Daption the thoracic vertebra 

 next in front of the pre-ilium is fused with the synsacrum. 



