224 THE VOYAGE OF H.M.S. CHALLENGER. 



pared with that of Spheniscus or of AjMnodytes ; in the trianguhxr or creseentic form of 

 the proventricular ghand ; in the length of the small intestine, which varies from nine to 

 eighteen times that of the vertebral column : in the fusion of a certain number of tracheal 

 rings, which are always ossified, to form the framework of the lower larynx ; in the 

 parallelism of the pessulus of the last tracheal ring with the long axis of the trachea ; iu 

 the close approximation of the vibrating membrane of the syrinx to the point of bifurca- 

 tion of the trachea ; and in the presence of a tracheal septum, which never exceeds in 

 length one-half of that of the trachea, and usually falls considerably short of it. 



If now it be asked whether any of the generic features oi Euchjptes above enumerated 

 are of themselves sufficient to distinguish the members of that genus from those which 

 constitute the genus Aptenodytes on the one hand, or the genus Spheniscus on the other, 

 the question may at ouce be answered in the affii-mative. Two of the characters above 

 enumerated are quite distinctive. Firstly, the form of the skull iis a, whole, and more 

 particularly the small development of the transverse temporal crest, together with the 

 lozenge-like form of the rami of the lower jaw bone, at once distinguish Evdyptes from 

 Spheniscus, while the relative shortness of the upper and lower mandibles similarly 

 distinguish Eudyptes from Aptenodytes. Secondly, the parallelism of the pessulus of the 

 last tracheal ring with the long axis of the trachea at once distinguishes Eudyp)tes from 

 Spheniscus, while the ossification of the rings which compose the framework of the syrinx, 

 and their immobility upon one another, strikingly contrast with the cartilaginous nature 

 and mobility of the syiingeal rings upon one another in Aptenodytes. 



Coming now to the consideration of the species which compose the genus Eudyptes, 

 the question arises, How many of the birds which I have had an opportunity of examin- 

 ing constitute clearly defined species ? 



I am aware that even ornithologists are not now disposed to admit that the three 

 varieties of Eudyptes chrysocome which inhabit Tristan d'Acunha, the Falkland Isles, 

 and Kerguelen Island, ought to be elevated to the rank of distinct species. Mr. 

 Sclater, the most recent writer on the subject, in his monograph on the birds obtained by 

 the Challenger expedition,^ groups these three varieties together, with the remark that 

 " on comparison of the series from these three localities, we cannot satisfactorily recognise 

 more than one species of Eock-hopper. The Ijird from Inaccessible Island has the 

 elongated superciliary plumes more produced ; those of the Falklands and Kerguelen 

 have them rather shorter." In this conclusion I agree with Mr. Sclater, who, basing 

 his conclusions upon an examination of skins, has arrived at the same conclusion as I 

 have after an exhaustive anatomical examination of one and all of these varieties. I 

 am strongly of opinion, however, that these three biixls constitute well-marked varieties 

 of the same species. 



A reference to the preceding pages shows that in Eudyptes ch7ysocome from Tristan 



1 Challenger Reports, Zoology, vol. ii. p. 129. 



