74 PROCEEDINGS OF THE ACADEMY OF 



The tibiae are denuded for some portion of their length. The tarsal scutel- 

 Ise are usually distinct, though fused in one genus. The toes are very long 

 and slender, the outer nearly or quite as long as the middle, the inner con- 

 siderably shorter. The hallux is exceedingly minute, almost rudimental in 

 character, having a short, straight, acute claw. The interdigital membranes 

 are rather narrow, but extend-quite to the claws. 



In examining collectively the species of the section thus characterized, we 

 find that they arrange themselves very naturally into two very trenchantly 

 defined groups. In the first of these, the legs are short ; the tibiae almost 

 wholly feathered; the tarsus scarcely longer than the middle toe; the claws 

 small, compressed and acute ; the colors uniformly dark, or only relieved by 

 white on the rump and crissum. In the second of these groups, the species 

 all stand high, the legs being unusually elongated ; the tibiae are naked for an 

 inch or more ; the tarsi are very much longer than the middle toe and claw; 

 the claws are all broad, depressed, obtuse, rounded. The tail is rounded or 

 forked : never cuieate. 



i. The first of these groups is composed of four genera :Occanodroma 

 (type Proc. furcala, Gm ), comprehending two species; Cy ><(. Mini, 



equal to Thalassidroma of authors, containing some four or five species : Ualo- 

 cyplena, Mini, a hitherto unknown genus, with a single species ; and Procel- 

 laria of Linnreus (as restricted by Bonaparte), whose type is the P. pelagica, 

 and which comprised several species closely allied to the last named. 



. The second grpup is represented by three genera: Oceanites of Keyser- 

 ling and Blasius, with Thai. Wilsoni of Bonaparte as type, and comprising 

 besides its type three other species; Fregetta, Bonaparte, comprising some 

 four species congeneric with tropica of Gould, and Pelagodroma, whose type 

 aud single species is the Procellaria fregata of Linnasus. 



I shall review these genera and their respective species in the order in 

 which they are mentioned above, discussing the various questions concerning 

 which there exists doubt or confusion, and then present a synopsis of the 

 whole subject, in accordance with the results which may be by this means 

 arrived at. 



?i I. OCEANODROMA, Reichenbach. 



This genus was founded by Prof. Reichenbach upon the old Procellaria 

 furcala of Gmclin. Its distinctive characters lie in its small, much com- 

 pressed, rather weak bill; in its comparatively very short wings, of which 

 the first primary is unusually abbreTiated, (being intermediate between the 

 fourth aud fifth), while the third is fully as long as the second : in its very 

 long, deeply-forked tail, with its broad central aud attenuated exterior 

 rectrices. In the proportions of the naked space of the tibia?, and of the 

 tarsus and toes it does not differ from several other genera of the section. 

 The middle toe with the claw is about as long as the tarsus. The colors are 

 peculiar, and only found in this ger.us. 



Two species of the genus are knowm to exist; both inhabiting the North 

 Pacific Ocean. 



1. OCEANODROMA FURCATA, Bp. CX (line!. 



This long and well known species has quite a profusion of a . generic 



as well as specific. First indicated by Gmelin, Syst. Nat. i. p. 561, in H&'S, 

 the name of Procellaria furcata, it was renamed Procellaria orientalis by 

 Pallas, Zoog. R isso As. ii. p. 315 (1S11), and afterwards called Thalassi- 

 droma cinerea by Gould. It is the < oma orientalis of Gray. Genera 

 of Birds, iii. 1849, pi. 17*; the Ocmmdroma oriental-is of Reichenbach, Syst. 

 Ar. xviii. fig. 24 1.".; and the 0. tndr furcata of Bonaparte, Conspectus 

 Avium, ii., 1S56", p. 194; which latter i . ! believe, its proper ation. 



The characters of the species are t<", r> i\\ known to require notice in this 

 connection. 



[March 



