| OCR Text |
Show 1899.] OSTEOLOGY OF THE TUBINARES. 397 (Pl. 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 of 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 tbe heraipterygoid from below. The dentary, angular, supra-angular, splenial, aud coronoid are all still traceable, but fusion of these elements has begun. iv. THE VERTEBEAL COLUMN. All the presynsacral vertebras are free, the thoracic are heteroccelous. 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 hyperapopbysis to the base of the anterior zygapophysis. Neural spines are well developed from the 2nd to the 5th vertebrae. The hyperapophyses of Diomedea are less well developed than in the Procellariidas. The thoracic vertebrae in the Procellariidas bear hypapophyses ; these are absent in the Diomedeidas. The anterior hypapophyses terminate anteriorly in a flattened plate. Below the neural canal the centra of the vertebrae bear each a deep depression, which in some-e. g., Ossifraga, Diomedea-becomes a large aperture into which open numerous pneumatic foramina. Similarly, in Ossifraga, Diomedea, and the larger Petrels there are large pneumatic apertures opening above the neural canal and below the transverse processes. The vertebras of sections A and B of the Procellariidas 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 few genera-e. g., Majaqueus, Priofinus, Diomedea-is there any distinct division into anterior and posterior renal fossas. In many genera, e. g. Puffinus, all traces of the original sacral vertebrae are lost. In Puffinus 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 vertebras (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 vertebras are 7 in number : making a total of 43 in all. In Fulmarus and Daption the thoracic vertebra next in front of the pre-ilium is fused with the synsacrum. |
