12 THE VOYAGE OF H.M.S CHALLENGER. 



abruptly from the forehead, and is truncated anteriorly, the single aperture so formed 

 looking upwards and forward (vide PI. I. figs. 1-5). In the Oceanitidse (e.g., fig. 8) the 

 aperture viewed from in front is nearly circular, and with scarcely any appearance of a 

 median septum. In the Procellarian genera, on the other hand (fig. 9), the aperture is 

 more oval and distinctly double, owing to the median septum (formed by the coalesced 

 inner walls of the narial tubes) being much less deeply, in a lateral view, excavated 

 anteriorly, and so appearing to a greater extent superficially. The other Procellariinse 

 repeat this form of nostril, though the septum becomes much thicker, so that the nostrils 

 open in them by two perfectly distinct apertures (vide fig. 7, where the nostrils of 

 Bulweria are shown). They might thus be said to be " platyrrhine," in opposition to the 

 *' catarrhine " Oceanitidse and other genera already mentioned. It is in Bulweria and 

 Majaqueus perhaps, that the nasal septum is broadest and most superficial ; in Prion it 

 is well developed ; in the remaining genera it is less near the external opening, but always 

 quite evident. In the genus Pvffinvs the septum is also broad, but the narial tubes are 

 so obliquely truncated that they hardly rise above the lateral outline of the beak ; their 

 openings are ovals, with their longer axis vertical or (Puffinus obscurus) oblique inwards. 

 In Pelecanoldes the nasal tubes are short and swollen externally ; the septum is 

 distinct, but not broad ; and the apertures, which are sinuated ovals directed antero- 

 posteriorly, look almost vertically upwards, their lateral outline being nearly parallel with 

 the axis of the upper jaw. 



In the Diomedeinre the nasal tubes are quite 



separate from each other, lying just at the lower 



margin of the " culminicorn." They are usually 



described as tubes with a distinct circular complete 



aperture, but on looking at this carefully, there 



may be seen (vide fig. 1) in front and below this 



tubular opening a deep cavity leading backwards 



and continuous behind, over the edge of the 



Fig. i.— Base of Beak of Diomcdca cxuians, to show apparent outer boundary of the aperture, with the 



the form and position of the nostril. general cavity of the tube, an infolding of the outer 



Avail of the latter forming the apparent outer wall of the tubular aperture. 



The nasal tubes of the Petrels are formed, it may be observed, by the elongation of the 

 cartilaginous walls of the nasal capsules. The upper and lower turbinal cartilages are well 

 developed ; the alinasal turbinal cartilage, on the other hand, is represented only by a 

 sbght ingrowth from the internal nasal wall. Such, at least, is the condition of these 

 parts in Majaqueus, the only form I have examined as regards these structures. 



The legs are always bare of feathers for some little distance above the tarsal joint, 

 the metatarsal scutellation extending upwards over the joint some little way, but disappear- 

 ing where the leg is covered by the feathers, and there replaced by simple skin. 



