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Show 468 MR. P. E. BEDDARD ON INTERCENTRA IN BIRDS. [May 4, TUBINARES. So far as my experience goes, all the Tubinares possess free intercentra in the caudal region; but m y experience is not of many species. In Diomedea melanophrys there are 6 free caudal vertebras. There is a minute osseous granule in front of the first of these. Then follow four intercentra increasing in size, and a single hypo-centrum ; the latter is perforated, and is thus a chevron-bone, while the last intercentrum is nearly perforated. In Procellaria glacialls there are the same number of intercentra, save that the first (the small bony granule) of Diomedea is absent, and that the last two (possibly three) have become hypocentra. The 2nd to the 4th are distinctly bifid, with a tendency for the ends to meet, and thus complete the chevron. Fregetta and Thalassidroma have also intercentra. S T E G A N O P O D E S. The only Steganopode in which 1 have found free intercentra is Phaethon. There are here three, gradually increasing in size and lying between the first and fourth free caudals. They are followed by three hypocentra, bifid at the apices. COLYMBI. In Colymhus septentrionalls (fig. 2) there are five vertebras between Fig. 2. Colymbus septentrionalis. Lateral (left-hand figure) and ventral aspects of caudai vertebras. (Lettering as in fig. 1.) |
