138 PROCEEDINGS OF THE ACADEMY OF 



robust bills, somewhat longer and more pointed wings, etc. These latter 

 cliaracters have been made typical of a distinct genus by Bonaparte. The 

 gradation, however, in these and all other features is so gradual, through 

 several intermediate forms, that I do not see how we are to draw the dividing 

 line. Bonaparte moreover includes in Cookilaria such a species as Solundri, 

 which is particularly a robust bird. 



Throwing out of consideration the fuliginous " Pterodromine " group, we 

 find tliat the other species of yE^f.relata adhere quite closely to a particular pat- 

 tern of coloration. When adult they are dark colored above, being of some 

 shade of brown or black, with more or less of an admixture of cinereous, and 

 generally have a white forehead. The color of the upper parts extends on the 

 sides of the breast ; otherwise the tinder parts are wholly white. When 

 young, the color of the under paits does not ditfer very notably as a general 

 rule from that of tlie upper: the white being ol)scured by a dusky, fuliginous 

 or cinereous clouding of the tips of all the featliers, the basal i^ortious of which 

 remain white. In general the younger the bird the more uniform, or more 

 tending towards fuliginous are its colors : while in adult life light and dark 

 colors occupy distinct areas, and are quite trenchantly defined. 



When we consider, therefore, the great change which the plumage under- 

 goes in the bird's progress towards maturity, togi_^ther with the similarity 

 that exists between corresponding ages, it will not appear surprising that not 

 only very numerous nominal species should have arisen, but that names of 

 species should have been frequently misapplied to others than those to which 

 they riglitly belong ; producing a confusion in the synonymy certainly not 

 surpassed, if indeed equalled, in any other genus in ornithology- A number 

 of the species were first brought into nutice by voyagers ; and when named by 

 professed naturalists it was at a time when the neces-ity of detailed descrip- 

 tions was not appreciated, so that the nice points of size and proportion which 

 really distinguish the species more than color, were rarely presented. The 

 oousequeuce is that it is now impossible to identify many of the older names 

 with any degree of certainty, except perhaps by incidental or collateral testi- 

 mony ; and to this day a great many identifications remain matters of opinion 

 rather than of fact. 



Nor is the confusion and uncertainty by any means less in the fuliginous 

 group which goes to compose this genus. Its components, so far as we know, 

 are in every age unicolor ; and are absolutely indistinguishable except by 

 form and dimensions. This alone would have been amjily sufficient for the 

 production of synomyms and malidentifications innumerable ; but this inevi- 

 table result is furthered by another fact. The "genus " Pterodroma is among 

 the yE.itrelalecE exactly what Neclris is among the Puffinecv ; 1. e. composed of 

 species ditferiug in no wise in form from yEstrclata or PuJ/hius, and which are 

 entirely fuliginous in color. Now the points of form separating the species of 

 " Pterodroma " from ^' Nectris " are by no means patent on a casual examina- 

 tion ; and hence, among the older writers we find many descriptions which 

 it is impossible to refer with any degree of certainty to one or the other genus, 

 of which, in short, we can say no more than that a fuliginous petrel formed 

 the subject of the article. Consequently, some synonyms have ever been oscil- 

 lating as to weight of authority between these two groups. 



I confess to a feeling of surprise, when, on examining critically species 

 typical of Bonaparte's genus Pttrodroinu, I could find absolutely no points of 

 form whereby it might be held separable from yJ'Jstrela'a. I do not think that 

 the skeleton will be found to present any tangible morphological characters, 

 critically examined in its minutest details of intermaxillary bone or phalanges ; 

 nor do the remiges or rectrices in their relative developments offer the 

 slightest discrepancies. We niu-jf have recourse therefore to color alone if we 

 would separate them ; and Bonaparte himself gives us no other character 



[May, 



