Birds mhabiting the Southern Ocean, 291 



Ocean — viz., P. pamirostris, Peale, by P. cooki, Gray; and P. 

 rostrata, Peale, by P. lessoni, Garn. ; they both, however, differ 

 more in colour from their types than the Arctic ones do from 

 theirs. Thalassidroma lineata, Peale, also from the torrid zone of 

 the Pacific, is a representative species of T. melanog aster ^ Gould. 



The shape of the beak of the Petrels is another point 

 well worthy of notice, so formidable is it in appearance, so 

 harmless in reality j the bite of the Albatros even being at- 

 tended with but little inconvenience, unless the point of the 

 beak happens to catch the hand, as the whole of the inner parts 

 are quite soft, and yield to a slight pressure of the finger. The 

 natural food of the Petrel tribe consists of small fish, the shell- 

 less molluscs, small crustaceans, Medusce, &c., which are swal- 

 lowed whole, and they do not therefore require a sharp beak 

 fitted for cutting or tearing ; for, although they may now and then 

 regale themselves on the body of a dead seal or whale, it is 

 evident that before sealers and whalers existed their opportunities 

 for doing so must have been few and far between — perhaps not 

 more than once in their lives; and if dead whales and seals 

 were their usual food they would find the tube, formed by the 

 nostrils on the top of the beak of many of the species, very dis- 

 advantageous, as it must prevent them striking their beaks deep 

 into the blubber. Of what use, then, it may be asked, is the 

 sharp, curved point of the beak ? I believe it to be of little or 

 no use ; but that it simply marks their close relation to, per- 

 haps their direct descent from, the Skuas (Lestris), who use it 

 in their attacks upon Gulls. It cannot be said that those 

 species which burrow require a harder beak than the Sand- 

 Martin, or that those species which throw up mounds require 

 one stronger or more sharply curved than the Flamingo ; and it 

 is certain that, for the capture of their prey, the hooked point is 

 no more wanted in the Petrels than in the Kingfishers, Herons, 

 Divers, &c., and not so much so as in the Gulls {Larus), some 

 of which occasionally kill and devour small birds. This opinion 

 is further strengthened by the fact that the young P. gigantea 

 very much resembles in plumage the young L. catarrhactes, and 

 it also inherits its habit of chasing other birds. 



It is well known that all crepuscular birds have some organ 



x2 



