NATURAL SCIENCES OF PHILADELPHIA. 85 



seems useless to exchange one doubtful opinion for another, I have preferred 

 to consider both species as valid, until an opportunity be afforded of deter- 

 mining the question with certainty. 



4. Oceanites gracilis, Coues ex Elliot. 



Tkalassidroma gracilis, D. G. Elliot, Sclater's Ibis, 1859, p. 391. "Plumage 

 sooty black. Quill feathers brown. Secondary coverts margined with light 

 brown. Ramp, upper tail coverts and middle of abdomen, white. Tail black, 

 the two outer feathers with a white mark on the lower half of the inner web, 

 growing narrower as it descends ; lower half of the shafts white, the rest 

 black. Under tail coverts white margined with black. Breast sooty. Bill 

 black. Tarsi and feet very long and slender, black. Length 5-90 inches ; 

 wing 5-22 ; tail 2-40 ; bill -40 ; tarsus 1-20." 



Habitat. Coast of Chili. 



In general characters this species seems closely allied to Oceanites lineata, and 

 the pattern of coloration is, in many respects, very similar. The dimensions 

 of the bird, however, will at once separate it from that species ; for the wing 

 is more than half an inch shorter, the tail fully as much less, and the bill, 

 tarsus and toes are proportionally as much smaller in dimensions. As already 

 remarked, it comes much nearer to the 0. segethi, and is very possibly the 

 same bird. In the event of this proving to be the case, gracilis, Elliot, has 

 priority over segcthi, Ph. et L., and must be retained as the name of the 

 species. 



VII. FREGETTA, Bp. 



This well marked genus, as limited by its author, Bonaparte, contains sev- 

 eral species, all more or less closely allied to each other, and agreeing in the 

 possession of the following generic characters : The bill is small and short,. 

 measuriag in length hardly half that of the skull ; about as high as broad 

 at the base, the sides converging rapidly toward a somewhat compressed, at- 

 tenuated and decurved tip. The nasal tubes are stout, short and elevated 

 towards their extremities. The culmen and commissure are both much de- 

 curved. The wings are rather elongated, reaching a little beyond the tail ; 

 the second primary is longest, the third nearly equal ; the first generally 

 between the third and fourth. The tail is long, nearly square, but sometimes 

 more or less emarginate ; the rectrices all exceedingly broad to their very 

 tips, which are subtruncated. The legs are long and stout; the tibiae naked 

 for a considerable space ; the tarsi much exceed in length the toes, which 

 latter are very short, unusually stout, and connected by rather narrow webs. 

 The species are all of rather large size, and stout form, and are bicolor, the 

 dark and light colors occupying distinct areas. The type of the genus is the 

 Thalasxidroma tropica, Gould, which, with the other species, chiefly inhabit the 

 intertropical and southern seas. 



The genus is so well marked as to require special comparison with no 

 other. The following are the species composing it with which I am ac- 

 quainted : 

 1. Fregetta tropica, Bp. ex Gould. 



First described by Gould, Ann. et Magaz. Nat. Hist. vol. xiii. p 366, under 

 the name of Thalassidroma tropica, this species is referred to its proper genus 

 by Bonaparte, in his Conspectus Generum Avium, p. 197, and also in his 

 Conspectus Gaviarium, p. 797 of the Comptes Rendus for 1856. If there be 

 other synonyms of the species, I have not met with them. 



It is the largest species of the genus, measuring 8'75 to 9-00 inches in 

 length. The tail is more forked than in the other representatives of the 

 genus, the depth of the emargination being f of an inch. The bill measures 

 a little more than ^ the length of the tarsus and it is rather stout, especially 

 at the base, where it is broader than high. The tarsus varies from If to If 

 of an inch in length ; the middle toe with its claw \\ inches, or a little more, 



1864.] 



