694 S. SUPERCILIARIS VAR. ANTILLARUM, LEAST TRRN. 



The primaries are ahont as described last. The tail is colored much as in summer, but 

 the lateral ieiithers have not the elongation that they acquire during that season. 



The hnmatitre u-itiUr plumaye, or that of a young bird -which has just conijileted its 

 first autumn moult, diifers from the above as follows: It is somewbat smaller, with 

 considerably weaker bill, the basal portions of which are still more or less dirty Hesh- 

 color. The forehead and vertex are rather giayish-white than i)ure white, and the 

 brownish-black of the nape is interrupted with light grayish. Tiie uniformity of the 

 colors of the upper ]iarts is interfered with by the still remaining lighter tips of most 

 of the feathers, while some may yet retain the brownish subapical sjiots of the avis 

 liorvoliva. The tail has still some traces of dark subapical spots. It is only in early 

 winter thnt this particular plumage can be seen, for toward spring the birds are 

 hardly to be distinguished from the adults. 



We have yet to describe the bird-of the-year in July and August, before its first 

 moult ; the following is the pluusage of the — 



Avis hor )wi ill a. — BiW nearly as stout at the base as in the adults, but shorter, more 

 obtuse, with illy-developed symphyseal eminence; brown.ish-black ; under mandible 

 basally dull liesh. Frous mostly white ; the vertex and occiput variegated with 

 brownish-black and white, the former color mostly aggregated into a. post-ocular j)atch. 

 Dorsum and alar tectrices lightly washed with the pearl-gray of the adults, but the 

 coutiimity of this color greatly interiupted by hastate or crescentie spots of brown, 

 which mottle the Avhole upper parts, one or more being on each feather. Primaries 

 grayish-black, growing lighter from without inward. Their inner webs are bordered 

 with white, broadest on the outer primary, growing narrower and longeron the others 

 till, on the inner ones, it goes quite around the tip of the feather on to the outer web; 

 outer web of first j)riii)ary, and shafts of all the primaries, pure black superiorly, pure 

 white inferiorly. Tail deeply emarginate, the lateral feathers scarcely elongated ; 

 pearl-blue, deepening towards the lips of the rectrices into dusky-gray, the extreme 

 apices again white. Whole under parts pure white. Size scmiewhat less than the adults. 



Dimensions of 1}ie adult. — Length, about 9; extent, 20; wing, 0.60; tail 3.50, its fork 

 1.75; bill along culmen, l.'iO ; depth at base, 0.28; tarsus, O.tiU ; middle toe and claw, 

 0.72. Youiif/ correspondingly smaller in all dimensions: Length, about 8.50; wing, 

 6.35 ; tail, 3.25 ; bill down sometimes to 1. 



Other variations. — As in all Terns, there is a notable variation in the length and 

 stoutness of the bill ; but the largest I have seen do not equal those of either viinuta 

 or siqjerciliaris proper. But v.hen we come to compare tyi)ical siipcrciHaris of South 

 America with miniita, we find no notable difierence; so that size of the bill can only 

 be used to distinguish the North American variety of siq)crciJiaris from minxta — not 

 whole American form from its European representative. In color, the bill of var. 

 aniillarum usually presents us with a black tip one-eighth to one-fourth of an inch long ; 

 while in sin)crciruiris the bill is wholly yellow. But, in enumerating the dilierent 

 points of siqierc.il iaris and aiiliUarnm, Messrs. Sclater and Salvin, who separate the two, 

 have overlooked the tact, which I only lately learned myself, that in a certain percent- 

 age of antillariim itself the bill is wholly yellow, and that sometimes the bill of siqier- 

 ciliaris is dark at the ti)).* In examining a great many fresh siiecimens oi' antillarum, 



* This is the case, for example, with No. 21082, from the Parana, South America, in 

 which the bill is yellow, clouded with olivaceous on the under mandible, and with the 

 tip brownish for nearly a fourth of an inch. The bill is notably longer and larger 

 than in var. aiitiUarnm — almost 1.40 along culmen, and 0.30 deep at base. The bird is 

 also larger — the wing 7.15, or about an inch longer than usual in niitinariim. 



A specimen of S. nereis, Gould, from New Zealand (No. 60268, Dr. J. Haast), agrees 

 substantially with Eurojtean minuta, in tlie pearly-gray not extending on the tail, and 

 large dark-tipped bill. The bill is, however, even stouter, especially deeper at the 

 base than in minuta, and the general size is jiotably greater; Aving, 7.10; bill 1.25 

 along culmen, 0.32 deep at base. 



S. exiJis of Tschudi (Peru) I have not seen. As understood by Messrs. Sclater and 

 Salvin (who refer to it S. loricata, Pii. «Sr Landij., Wieg. Arch. 1863, 124, Bay of Arica), 

 it appears decidedly diflerent from the rest. Without considering the <iuestiou of posi- 

 tive taxonomic rank, the several forms just mentioned may be thus tabulated : 



A. Entirely white below. 



a. Pearly of mantle not extending on tail, which is white. 



1. Smaller; wing, uuderT; bill, about 0.25 deep at base minuta. 



2. Larger; wing, 7 or more; bill, 0.30 or more at base nereis. 



h. Pearly of mantle extending uninterrupted on tail. 



3. Smaller; wing, under 7; bill, under 1.25, usually black 



tipped antillarum. 



4. Larger; wing, over 7; bill, over 1.25, seldom black tipped.. supLreiliaris. 



B. " Gray " below ; bill very slender, its terminal half black cxilis. 



