Bird Caves uf the Bermudas. 631 



in the latter this line or distance equals but 4*4- centi- 

 metres. Prom apex to apex of the coracoidal processes, 

 P. mcgalli measures 3'3 centimetres, and P. Iherminiei'i but 

 2 5 centimetres. 



Upon comparing this sternum with the sternum of 

 Puffinus major (No. 18076, Coll. U.S. Nat. Mus.), the 

 latter is seen to be a species very considerably larger than 

 the one here being described. I have also compared it with 

 the sterna of Puffinus creatopus, P. borealis, P. griseus, and 

 others, but it departs more or less from all of them. 



In the collection of the U.S. National Museum, there is 

 a Shearwater (No. 19385) labelled "Puffinus gavia, San 

 Diego, Cal." Sharpe, in his 'Hand-list' (vol. i. p. 124), 

 restricts the range of this species to " New Zealand and 

 Australia." It is not listed in the A.O.U. Check-List 

 (1910). This "P. gavia'' was a bird of almost exactly the 

 same size as Puffinus mcgalli, and its sternum, measured as 

 above, has a length of 5*6 cm., while its width, measured 

 as above, equals 3*45 cm. It is not at all likely that the 

 stt-rnum here under consideration belonged to an individual 

 of that species — that is, it did not belong to a P. gavia. 



Sometimes the plumage and other external characters of 

 species of the same genus of birds of the same size are 

 strikingly different, while the skeletons of any two of those 

 species may be indistinguishable. There is no reason to 

 believe but that this may have been true of any two species 

 of Puffinus — the two species compared being of the same 

 size. For example, one would have to be very expert indeed 

 in order to be able to distinguish the sternum of a specimen 

 of Dendroica coronata from the same bone taken from a 

 specimen of Dendroica auduboni — age and sex in the two 

 individuals being the same. Had we skins of these two 

 species, however, there would be no difficulty in identifying 

 them, and pronouncing at once as to which was which. 

 This is the case with respect to the bones of the skeleton of 

 a great many birds of the existing avifauna ; still, the 

 expert osteologist, who may have been a constant student 

 of the subject for a lifetime, and who has handled large 



