NATURAL SCIENCES OF PHILADELPHIA, 125 



brown , without the slightest tinge of ashy; a little darker on the rump, so dark 

 as to be brownish black on the wing coverts and tertials ; the extreme tips of 

 which latter are somewhat paler. The primaries are lustrous brownish black 

 on their outer webs and at their tips ; and their inner webs are but little 

 paler ; their shafts are on their superior aspect black, becoming brownish ba- 

 sally ; their inferior aspects also black, but with a delicate white line running 

 medianly two-thirds their whole length. The rectrices are colored like the 

 primaries ; their shafts are brownish black. The entire under wing coverts 

 are white ; the purity and continuity of which is, however, interrupted by 

 some grayish brown marbling. The under parts generally are much lighter 

 thau the upper, and of a grayish rather than brownish fuliginous, this color 

 passing on the throat and chin gradually into a somewhat grayish cinereous 

 hue. The short anterior under tail coverts are light grayish brown ; the loug 

 posterior ones are more of a brownish fuliginous. There is a delicate touch of 

 white on the under eyelid. 



Dimensions. Length of bill along culmen 1-70; from feathers on side of 

 lower mandible to its top, 1'60 ; length of nasal tubes, -45 ; height of bill at 

 base, -45 ; width about the same. Wing, from the carpus, 11-00 ; tail, 4-25 ; 

 graduation of lateral rectrices, *90 ; tarsus, 2-00 ; middle toe and claw, 2-40 ; 

 outer do., 2 30 ; inner do., 1"90. 



It may seem somewhat improbable that a species of Nectris has remained to 

 this late day undescribed ; but the subject of the present article differs in so 

 many particulars from any known bird of the genus, that I have not the 

 slightest hesitation in presenting it as new. It is most closely allied to fuli- 

 ginosa, Strickl., but differs from it, as well as from carneipes and tenuirostris, 

 in many very tangible points. The combination of the wholly dark bill, with 

 the coloration of the feet, as above described, the white on the under surfaces 

 of the wings, together with its own particular dimensions, readily character- 

 ize it among its congeners. The following detailed comparison of it with each 

 may serve to define its relationships more explicitly. 



With the general colors of fuliginosus, especially as regards the wholly 

 dark bill, it differs in the conspicuous white under wing coverts, only a little 

 obscured by grayish brown, and in the different tints and pattern of the feet. 

 (Compare original descriptions of each species.) It is much smaller than that 

 species, to wit: the length about fifteen inches, (as near as I can judge from 

 the skin,) instead of eighteen ; the tarsus barely two inches, instead of two 

 and a quarter ; the toes less in proportion ; and the wing eleven, instead of 

 twelve inches. 



It is more nearly of the same size as carneipes, but in that species the 

 "whole of the plumage is chocolate black;" the bill is flesh colored, except 

 on the culmen and at the tip, whereas in my bird it is wholly dark. The feet 

 of car in ipes are wholly " yellowish flesh color," while in amaurosoma the ex- 

 ternal aspect of the tarsus and the outer toe are brownish white. 



The species hardly requires any comparison with tenuirostris or brevicauda, 

 the notable differences of color alone, or of dimensions alone, at once separa- 

 ting them. The bill of amaurosoma measures about 1'70 inches; that of 

 tenuiros ris 1*20 ; the wing 11, instead of 10 inches ; the tail 4*75 to 5 "00, in- 

 stead of 350, etc. The general color of tenuirostris is a deep smoky black, 

 with a tinge of ashy ; that of amaurosoma brownish fuliginous. Compare also 

 the descriptions given in this paper of the colors of the bill and feet. There 

 is just about the same amount of whitish on the under surfaces of the wings 

 of the two species. 



The type of this species, now in the Smithsonian collection, was procured by 

 Mr. John Xantus at Cape St. Lucas, Lower California, August 18th, 1^60. It 

 is there apparently the representative of fuliginosus, as my opisthomelas is of 

 obscurus. 



1864.] 



