468 



MR. F, K. BEDUAHD ON IKTEROEXXEA. IN BIRDS. [May 4, 



TUBINAEES. 



So far as my experience goes, all the Tubinares possess free intef- 

 centra in the caudal region ; but my experience is not of many 

 species. 



In Diomedea melanoplirys there are 6 free caudal vertebrae. 

 There is a minute osseous granule in front of the first of these. 

 Then follow four intereentra increasing in size, and a single hypo- 

 centrum : the latter is perforated, and is thus a chevron-bone, while 

 the last interceutrum is nearly perforated. In Procettaria glacialis 

 there are the same number of intereentra, 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 

 intereentra. 



Steganopodes. 



The only Steganopode in which 1 have found free intereentra 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. 



COLXMBI. 



In Colymbus sejitenttionalis (fig. 2) there are five vertebrae between 



rig. 2. 



Colymbus scptentriotialis. 



Lateral (left-hand figure) and ventral aspects of 

 caudal vertebrae. 



(Lettering as in fig. 1.) 



