NATURAL SCIENCES OF PHILADELPHIA. 553 



outer web. The tail is not deeply forked, but simply einarginate, 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 105 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 9 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 claimg 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 

 be 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 

 ever 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 meme dans 1'Amerique septentrionale. Les voyageurs au Brezil 

 ont aussi trouve dans ces contrees une petite hirondelle-de-mer modelee sur les 

 formes de la notre. Mais elle forme une espece distincte, bien caracterizee par 

 son bee plus robuste, qui est entierement 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. Voy. 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 witb 



1862.] 



* Man. d'Orn. vol. ii. p. 753. 



