378 ON THE PETRELS COLLECTED DURING 



As regards the number of rectrices in the Tubinares, twelve is the 

 ordinary number in both families, and this is never reduced *, and only 

 in a few instances exceeded. Fulmarus and Daption have fourteen tail- 

 feathers, as already pointed out by Mtzsch, and the same is the case in 

 Thalassceca ; Ossifraga has as many as sixteen. Aeipetes antarcticus (in 

 both the specimens examined by me) has, on the other hand, unlike 

 Thalassceca, the normal number of twelve. 



The number of primary remiges is always ten, but that of the 

 secondaries varies. The number of these in the Oceanitidse is always ten ; 

 in the ProcellariidaD it is never, even in the smal]est forms (Pelecano'ides, 

 Cymochorea, Halocyptena, Procellaria\ less than thirteen. Bulweria has 

 twenty, which is about the average number throughout the group, 

 increasing, however, in the larger forms to twenty-nine (Ossifraga, 

 Thalassiarche), thirty (Diomedea brachyura), and even, in the largest of 

 all, Diomedea exulans, to thirty-seven f. The pollex never has the claw 

 so often present in birds on that digit. 



As regards the distribution of the tracts of contour-feathers, I may 

 quote Nitzsch's general description (Pterylography, Ray Soc. ed. pp. 

 143, 144) : " In this family the tract-formation of Lestris is elevated 

 into the type of a group, undergoing scarcely any change in the form of 

 the inferior tract, but showing some little modification in the dorsal 

 Zool. ChalL tract. We find, therefore, on the head a uniformly dense plumage, from 



Bzp.Yol.iY, 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 still 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 pectoraUs major. Here it is divided by a space startiDg f rorn 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 scapula, into two limbs. In most 

 of the Tubinares these limbs pass uninterruptedly into the posterior half 



* Mtzsch (Pterylogr. Ray Soc. ed. p. 141) thought that the smaller species of 

 Petrels had but ten tail-feathers, but such is not in reality the case. 



t Nitzsch even describes the species as having as many as forty secondaries. The 

 total alar expanse of the specimen I counted this number in was 9 feet 7* inches. 



