THE VOYAGE OF THE 4 CHALLENGER.' 431 



Cymockorea one only, and Halocyptena t as already mentioned, has them 

 quite absent. 



The position of Pelecanoides has already been fully discussed ; it stands 

 quite per se, though presumably derived from a stem common to it and 

 the remaining Procellariinae, which must have diverged from the less 

 specialized one now represented by the Procellaria-group. 



Prion (with which Halobcena is probably to be associated) represents a 

 third minor group, much specialized as regards its peculiarly broad beak 

 with its fringe of lamellae, whilst in its tensor-patagii arrangement and 

 syrinx it is not highly developed. 



The two genera Pagodroma and Daption seem very central as regards 

 their relationships, which seem to be with Prion (as indicated chiefly by 

 the rudimentary lamellae of Daption) on the one hand, and with the Zool. Chall. 

 Fulmars on the other, Aeipetes * being the less specialized of these, both jj^i'jj'gj 

 as regards its imperfect trachea! 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. 401) in that of Pago- 

 droma, and all four genera (Fulmarus, Thalassoeca, Ossifraga, and Aeipetes} 

 agree in the general disposition of the ttnsor patagii, which has no ossicles, 

 in the more or less rudimentary os uncmatuin, in the tendency to anchy- 

 losis of the lachrymal and frontal, in the shape of the tongue and of 

 more or less well-developed lamellae on the bill, and in having four more 

 or less complete, but never deep, sternal emarginations. 



Aeipetes is, on the whole, the least specialized of the Fulmarine group 

 in the most limited sense. This includes besides Thalassoeca, Fulmarus, 

 and Ossifraya, which last, on account of its great size, peculiar syrinx, 

 and sixteen rectrices, may be considered the culminating point in this 

 direction of the Procellariidse. 



The remaining genera, (Estrelata, Pujfinus, Adamastor, Majaqueus, and 

 Bulweria, are also apparently closely related to each other, the first and 

 last named being perhaps least so. All agree in having a deeply four- ibid. p. 0. 

 notched sternum, in having well-developed uncinate bones, in the posses- 

 sion of one or t\vo accessory wing -ossicles developed in the termination 



* I propose to make a genus under this name, for the reception of the Procettaria 

 antarctica of Gmelin (Sy^t. Nat. 1788, vol. i. p. 505), which has usually been considered 

 congeneric with Thalasxceca, the type (and only representative) of which is Thalassoeca 

 ylacialoides. For the latter bird also was instituted Houibron and Jacquinot's genus 

 Priocella (s. c. vol. iii. p. 148). Aeipetes is easily distinguishable from Thalassoeca by 

 the much shorter and stouter bill, and differently shaped nasal tubes, as will be best 

 understood from the accompanying figures (figs. 31,32, p. 432). The number of rec- 

 t rices is also different (twelve as compared to fourteen) ; the tracheal septum is incom- 

 plete, and the structure of the syrinx also quite different (fide supra, p. 404). The 

 coloration of the two forms is quite unlike. 



