<}'2 THE VOYAGE OF H.M.S. CHALLENGER. 



Most previous writers have considered the Petrels as more or less closely connected 

 with the Gulls (Laridae), hut the grounds for any such collocation are very slight, in my 

 judgment, now that the structure of the two groups is better known. 



The Gulls exhibit no trace of any of the characteristic peculiarities of the Petrels, 1 and 

 differ widely from them in the important feature of being schizorhinal. 2 The peculiar 

 disposition in two quite separate layers of the great pectoral muscle in the Tubinares is 

 quite unlike anything seen in the Gulls or their allies, whilst the large pectoralis 

 tertius of the Petrels is altogether unrepresented in the Laridaa. The character of 

 the caeca in the two groups is also quite different, and there are no special osteological 

 resemblances between the two groups so far as I can see, for the mere schizognathous 

 character of the palate is, we now know, not necessarily a mark of affinity. The 

 character of the young plumage, the condition of the young birds, and the number, 

 shape, and coloration of the eggs — points on which some stress may be laid in questions 

 of this kind — are totally dissimilar in the two groups, as indeed are the habits of the 

 adult birds themselves, though no doubt both are "web-footed" and more or less 

 pelagic in habit. Such resemblances, however, can* hardly be seriously considered as 

 indicating any real affinities. 3 



L'herminier, A. Milne-Edwards, and Huxley have all, in describing various points in 

 the osteology of the Tubinares, pointed out similarities of various kinds between their 

 osseous structure and that of various forms of the Steganopodes, though they still kept 

 them close to the Laridae. Eyton, on the other hand, places the various Petrels he 

 describes in the family " Pelecanidae," the Gulls forming a separate family by them- 

 selves. 



But no one will be prepared, I think, to dispute that the Steganopodes are allied to 

 the Herodiones, including under that name the Storks and Herons, with Scopms, only. 

 Thus, on osteological grounds alone, there is sufficient ground for placing the Tubinares 

 in the vicinity of the Steganopodes and Herodiones. And, in fact, neglecting the 

 desmognathous structure of the palate — the taxonomic value of which per se is becoming 

 more and more dubious as our knowledge of the structure of birds increases — there is little 

 in the characters assigned to the groups Pelargomorphas and Dysporomorphae by Professor 

 Huxley (I. c, p. 461) that is not applicable to the general Petrel type. 



The completely double great pectoral muscle is a characteristic only found, as already 

 •observed, in the Ciconiidaa, Cathartidse, the Steganopodes (except Phahierocorax), and 



1 I cannot understand Professor Huxley's remark (Proc. Zool. Soc, 1867, p. 455) that " the Gulls grade insensibly 

 into the Procellariid;e." 



• '/. Garrod, Coll. Papers, p. 128. 



3 No views regarding the affinities of the Petrels other than that to the Laridae already discussed, and that to 

 the Ciconiiform birds have, so far as I know, been seriously advanced by ornithological writers, Professor Garrod 

 having abandoned his early idea that the Tubinares were probably related remotely to the Anseres and their allies, 

 (r/. Coll. Papers, pp. 220 and 521). 



