694 S. SUPERCILIARIS VAR. ANTILLARUM, LEAST TERN. 



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

 the lateral fciathers have not the elorifjation that they acciuire during that season. 



The immature u-intcr plumage, or that of a young bird which has just completed its 

 first autumn moult, difters from the above as follows: It is somewhat smaller, with 

 considerably weaker bill, the basal portions of which are still more or Ic.'is dirty flesh- 

 color. The forehead and vertex are rather giayish-whito than pure white, and the 

 brownish-black of the nape is interrupted with light grayish. Tlio nniformif.y of the 

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

 of the feathers, while some may yet retain the brownish subai>ical spots of the aris 

 Tiornolina. The tail has still some traces of dark subapical spot.i. It is only in early 

 winter that this particular plumage can be seen, lor toward spring the birds are 

 hardly to be distinguished from the adults. 



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

 moult ; the Ibllowing is the plumage of the — 



Jris lioriiolina. — Bill nearly as stout at the base as in the adults, but shorter, more 

 obtuse, with illy-developed symphyseal eminence ; brownish-black ; under mandible 

 basally dull flesh. Frons mostly white : the vertex and occiput variegated with 

 brownish-black and white, the former color mostly aggregated into a post-oenlar patch. 

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

 continuity of this color greatly interiuj>ted by hastate or crescentie spots of brown, 

 which mottle the whole upper parts, one or more being on each feather. Primarica 

 grayish-black, growing lighter from without inward. Their inner wobs are bordenjd 

 with white, broadest on the outer primary, growing narrower and longer on 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 immary, and shafts of all the primaries, pure black snperlorly, pure 

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

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

 apices again white. Whole under parts pure white. Size somewhat less than f lie adults. 



Dimensions of the adult. — Length, about 9 ; extent, 20 ; wing, (i.Gti ; tail 3..50, its fork 

 1.75; bill along culmen, l.yO ; depth at base, 0.28; tarsus, O.fcitj ; middle toe and claw, 

 0.72. Touni) correspondingly smaller in all dimensions: Length, about 8.50; wing, 

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



Other rarialioiis. — 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 miitula 

 or siiperciViaris jjroper. But when we come to compare tyiiical superciliaris of South 

 America with minnta, we find no notable difi'erence; so that size of the bill can only 

 be used to distinguish the North American variety of superciliaris from miriula — not 

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

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

 while in svperciliaris the bill is wholly yellow. But, in enumerating the dilferent 

 points oi superciliaris and antillarum, Messrs. Sclater and Salvin, who separate the two, 

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

 age of avtillarum itself the bill is wholly yellow, and that soiuetinies the bill of nuper- 

 dlinria is dark at the tip.* In examining a great many fresh specimens oi antillarum, 



* This is the case, for example, with No. 210'!!2, 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 fcui th of an inch. The bill is notably l.jnger and larger 

 than in var. anlillarum — almo.st 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 antiUuriini. 



A specimen of S. nereis, Gould, from New Zealand (No. 6fi2()H, Dr. J. Haast), agrees 

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

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

 base than in minuta, and the general size is notably greater; wing, 7.10; bill 1.25 

 along culmen, 0.32 deep at base, 



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

 Salvin (who refer to it S. loricata, Ph. & Laxdii., Wieg. Arch. 1803, 124, Hay of Arioa), 

 it apjiears decidedly different from the rest. Without considering the question 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, under 7 ; bill, about 0.25 deep at base minnta. 



2, Larger; wing, 7 or more; bill, 0,30 or more at baae -nereis. 



b. Pearly of mantle extending uninterrupted on tail, 



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



tipped-.- antillarum, 



i. Larger; wing,over7; bill, over 1.25, seldom blacktipped-. suptrciliaris. 



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



