REPORT ON THE ANATOMY OF THE PETRELS. 59 
Daption) on the one hand, and with the Fulmars on the other, Aeipetes’ being the 
less specialised of these, both as regards its imperfect tracheal septum, and the number 
of rectrices. The type of syrinx so characteristic of the Fulmars is foreshadowed, as it 
were, as has been already pointed out (supra, p. 35) in that of Pagodroma, and all 
four genera (Fulmarus, Thalasswca, Ossifraga, and Acipetes) agree in the general 
disposition of the tensor patagiw, which has no ossicles, in the more or less rudimentary 
os uncinatum in the tendency to anchylosis of the lachrymal and frontal, in the shape 
of the tongue and of more or less well-developed lamella on the bill, and in having four 
more or less complete, but never deep, sternal emarginations. 
Aeipetes is, on the whole, the least specialised of the Fulmarine group in the most 
limited sense. This includes besides Thalasseca, Fulmarus, and Ossifraga, which last, 
Fig. 32. 
Fic. 31.—Beak of Thalasseca glacialoides. a. The aperture of the nasal tubes, 
from in front. Natural size. 
Fic. 32.—The same parts of Acipetes antarcticus. 
on account of its great size, peculiar syrinx, and sixteen rectrices, may be considered the 
culminating point in this direction of the Procellariidee. 
The remaining genera, Hstrelata, Puffinus, Adamastor, Majaqueus, and Bulweria 
are also apparently closely related to each other, the first and last named being perhaps 
1 T propose to make a genus under this name, for the reception of the Procellaria antarctica of Gmelin (Syst. Nat., 
1788, vol. i. p. 565), which has usually been considered congeneric with Thalassaca, the type (and only representative) 
of which is Thalasswca glacialoides. For the latter bird also was instituted Hombron and Jacquinot’s genus Priocella 
(s.c., vol. iii. p. 148). -Aezpetes is easily distinguishable from Thalasswca by the much shorter and stouter bill, and 
differently shaped nasal tubes, as will be best understood from the accompanying figures (figs. 31, 32). The number 
of rectrices is also different (twelve as compared to fourteen) ; the tracheal septum is incomplete, and the structure of 
the syrinx also quite different (vide supra, p. 37). The coloration of the two forms is quite unlike. 
