ORNITHOLOGICAL EXPLORATIONS. 185 



lo be the larger sjiecies. The oi>posito result of Taczanowski's table can 

 only be accounted for by supposing that tbe measurements of the two 

 species have been transposed in the same manner as those of the total 

 length and the stretch of the wings. 



Nobody, however, who has ever seen the adults of both species when 

 fresh, or nearly so, mistook them for being the same species. The diffi- 

 culty has arisen from the young plumage, in which both species are very 

 much like each other. In the adult of the present species the feather- 

 ing of the forehead does not reach the base of the bill, thus rendering 

 it very easily separable from Ph. pelagicus ; butin theyonug wrt/e {=M- 

 crktatns) the forehead is as fully feathered as m pelagicus. Nevertheless, 

 it is the outline of the feathering at the base of the bill which will fur- 

 nish us with the best character, as in the young pelagicus it forms a 

 well-pronounced malar apex below the angle of the mouth, while in 

 urile it runs down in nearly a straight line without forming so conspicu- 

 ous an apex. 



A difference in the wing formula, as supposed by Mr. Swinhoe, can- 

 not be verified in a large series, there being hardly two individuals of 

 exactly the same relation between the primaries. 



But also the young in the nest are rather easily distinguished even 



before they have got any feathers. I give the following remarks as 



I wrote them, with the downy young of both species, just taken out of 



their nests, before me : 



lu urUe the limit betweeu the whitish while in pelagicus thislimit is much more 

 color of the gular iiortiou and the lead- irregular and has a quite different out- 

 colored skin of the remaining portion of line, 

 the body is very distinctly defined, 



The dusky down of wn7e is tipi^ed with the down in pelagicus being uniform 

 brownish gray, black, so as to give the whole bird a much 



darker appearance. 



On the outside of the thighs is a large while white down is altogether missing 

 spot dotted with white down, • in pelagicus. 



Of structural differences, is especially to compared with the much narrower shape 

 be mentioned, in «riiethe greater breadth of the l)ill at base in pelagicus. 

 of the bill at base. 



Even the a^^'^ of the two species cannot be confounded. Not only are 



those of tiriJe considerably larger than those of 7>eZ^rr/?'c».s, but the green 



color, when looked at through the shell, is totally diiferent, being much 



more bluish in the former, against yellowish in the latter. 



