NATURAL SCIENCES OF PHILADELPHIA. 
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outer web. The tail is not deeply forked, but simply emarginate, the difference 
being about that which attains between the adult and young of Hirundo horreo- 
rum. I have never seen it of quite the shape figured by Audubon ; but in his 
plate it is very accurately colored. 
This species is so very distinct from S. minuta , that it is a little singular that 
they should ever have been confounded. The following are the 
Differential Diagnoses of the American and European birds. 
S. minuta. — Bill along the culmen 1*20 inches, height at base -27 ; width of 
frontal lunula '40. Rump, upper tail coverts and tail pure white, in marked 
contrast to the pearl blue of the back and wings. 
S. antillarum. — Bill along culmen 1-05 inches, height at base *25; width of 
frontal lunula '30. Pearl blue of upper parts continued uninterruptedly on to 
the rump, tail coverts and tail. 
These differences are all I can discover between the two species ; quite enough, 
however, to permanently separate them. Nuttall states that the “ Silvery 
Tern is about to 10 inches long; the European species 8 to 8-£ only." It is 
difficult to determine the exact length of a species from dried skins ; but in this 
case it is certain that no such difference exists. In fact, judging from the wings 
and tarsi, — parts which do not change in dimensions in drying, — the two are 
nearly or quite identical in size; and I am sure that the difference, if any, is 
not greater than is found between individuals of either species. Both appear 
to range from eight to nine inches in length. I cannot appreciate the difference 
in the color of the upper parts mentioned by Nuttall. 
But, while our pretty little Tern thus rejoices, in unimpeachable claims to 
specific distinction, it has not been equally fortunate in retaining for any length 
of time undisputed possession of a title of its own. By the earlier writers on 
North American Ornithology it was confounded with the European bird, and 
called Sterna minuta , Linn. Nuttall, in 1834, was the first to vindicate its claims 
to specific distinction from its European analogue. This author, however, while 
he gives correctly enough its essential characters, commits the grave error of 
referring it to the Brazilian S. argentea of Prince Maximilian, — quite a different 
bird. Nuttall appears to have made the mistake in this wise. He evidently 
never examined a specimen of S. argentea ; for he says, “ That our bird is that 
of Brazil we have no further evidence than the slight notice of Temminck.” 
Now Temminck’s* remark is as follows: “Cette espece,” — S. minuta , — “ est 
absolument la merae dans l’Amerique septentrionale. Les voyageurs au Brezil 
ont aussi trouvb dans ces contrees une petite hirondelle-de-mer modelee sur les 
formes de la notre. Mais elle forme une esphce distincte, bien caracterizee par 
son bee plus robuste, qui est entikrement d’un beau jaune clair ; les distributions 
des couleurs offrent aussi quelques disparites. Le prince de Nieuweid indique 
cette espece sous le nom de Sterna argentea. Vo y. v. i. p. 67.” With only this 
brief indication to guide him, and impressed with the different distribution of 
the colors of the upper parts of S. minuta and antillarum , Nuttall might readily 
overlook the discrepancies mentioned in the size of the bill, and in this manner 
refer the American bird to the Brazilian. 
In the Proceedings of the Philadelphia Academy for 1848, Dr. Gambel points 
out the distinctive features of the present species and the S. argentea , and our 
bird being thus left without a name, he applies to it the exceedingly appropriate 
one of S.frenata, by which it has been known from that date up to the present 
time. I am therefore very reluctant to supersede it by any other ; but the 
Sternula antillarum of Lesson undoubtedly refers to the present species, and 
has priority in point of date. Lesson’s description (vide op. cit.) is essentially 
as follows : “Differs from S. minuta in its shorter bill , of orange color, tipped 
with black; the white frontal band narrower. Two outer quills bordered with 
1862.] 
* Man. d’Orn. vol. ii. p. 753. 
