REPORT ON THE ANATOMY OF THE PETRELS. 15- 



tract. We find, therefore, on the head a uniformly dense plumage, from which the two 

 principal tracts issue. The latter are separated from each other by the two lateral neck- 

 spaces, which extend high up, nearly to the head. The inferior tract is divided near the- 

 head, becomes of considerable breadth whilst stdl on the neck, and passes in this condition 

 on to the breast, the surface of which is covered by each band in a rather broad, parallel- 

 sided form, emitting no branch as far as the margin of the musculus pectoralis major. 

 Here it is divided by a space starting from the knee-covert in such a manner that a short 

 continuation of the tract, which is to be regarded as an outer branch, passes near the 

 knee into the lateral space of the trunk, runs on over the thigh, and soon afterwards 

 terminates. The other, inner branch, which represents the main band, then proceeds on 

 the belly, turns in a somewhat arcuated form outwards, dilates considerably in the 

 middle of the bow, and terminates near the anus. . . . The dorsal tract is at first 

 broad, becomes narrower towards the middle of the neck, then expands at the shoulder, 

 and divides at that point, or from the middle of the scapulas, into two limbs. In 

 most of the Tubinares these limbs pass uninterruptedly into the posterior half of the 

 dorsal tract ; and this circumstance forms their family character as distinguished from the 

 Longipennes. In the present group the posterior half of the dorsal tract encloses a 

 longitudinal space as far as the caudal pit, dilates a little outwardly on the pelvis, and 

 thus usually becomes united with the very oblique lumbar tracts, and grows rather strong 

 in the simple uropygial band, also covering the base of the oil-gland." 



Nitzsch had no opportunity of examining the pterylosis of Pelecanoldes, nor any of 

 the Oceanitidse. His remarks were based on examination of Fulmarus glacialis, Daption 

 capensis, Ossifraga gigantea, Procellaria pelagica, Hcdobcena ccerulea, Puffinus obscurus, 

 and Diomedea exulans and cMororhyncha. Nitzsch points out certain peculiarities in the 

 latter genus, the most important of these being the division of the dorsal tract into two 

 quite separate parts — an anterior stronger part, ending in an interscapular fork, and a 

 posterior, weaker, dilated part. The lumbar tracts he describes as weak and uniserial. I 

 find this division of the dorsal tract to hold good in Diomedea exulans and brachyura, as 

 well as in Thcdassiarche cidminata, though the break is not very obvious, and chiefly 

 marked by the difference in strength of the feathers. In a nestling of Phabetria, how- 

 ever, there is no such break apparent ; though the dorsal tract anteriorly is stronger, it 

 passes behind into the posterior part, and the same condition, as is pointed out by Nitzsch, 

 obtains in Ossifraga. The lumbar tracts also can hardly be strictly described as uniserial, 

 as they tend to coalesce, by rows of interposed contour-feathers, with the external borders 

 of the dorsal tract, no very obvious demarcation separating the two. 



Pelecanoldes and the Oceanitidse quite conform to the general type of the group, and 

 indeed the only at all obvious difference in this, beyond those already mentioned, lies in 

 the greater or less amount of the connection between the lumbar and dorsal tracts, this 

 being almost nil in Cymochorea and Procellaria, and considerable in the larger forms, 



