G66 STERNA AN6LICA, GULL-BILLED TEEN. 



ean. I have been unable to detect any discrepancieB, nor do I think that any charac- 

 ters have ever been assigned to our bird. Wilson, in liia description, does not compare 

 it with the European, doubtless for the best of reasons — that he did not know it. His 

 name, however, has been generally adopted for our bird since the time of its use in that 

 connection by Bonaparte, in 1838. 



Synonymy. — The name angllca is rather an unfortunate one, since the bird, though 

 then described from specimeos shot in England, seems to be much less abundant in that 

 country than in most other places where found. As, however, there is implied in the 

 name no actual geographical error, it is unnecessary to change it, as was done by 

 Macgillivray. Several names, additional to those above cited, appear to belong here, 

 but as I have made no critical examination of these supposed species, I do not here 

 consider them. Schlegel unites a number of current species, and is probably right in 

 so doing. 



Subgenus Thalassetjs, Boie. 



< sterna, Pall., Nov. Coram. Petrop. xiv. 



< ThaUsseus, BoiB, Isis, 1822, 563 (type S. caspia, Pall.).— Coues, Rev. Sterninw N. A. 



Pr. A. N. S. Phila. Dec. 1862, 536. 

 > Sydroprogne, Kaup, Sk. Ent. Eur. Thlerw. 1829, 91. {S. caspia.) 

 y. Sylochelidon, Beehm, Vog. Deutsch. 1831, 770. (S. caspia.) 

 S^Helopus, Wagl., Isis, 1832, 1224. (S. caspia.) 

 p- Aciochelidon, Kaup, Sk. Ent. Eur. Thierw. 1829, 31. (Sterna cantiaca.) 



Gen. chak. Bill as long as, or longer than, the head ; robust ; its height at the base 

 a fourth to a third of its length along culmen. Culmen variable in amount of curva^ 

 ture, from nearly straight to very convex. Gonys of variable length. Wings only 

 moderately long for this subfamily ; pointed, but the first primary not surpassing the 

 second by as much as the second does the third. Tail moderate or very short, in the 

 type of the genus greatly abbreviated, being contained three times in the wing from 

 the carpus, and but moderately emarginate. In other species more elongated and quite 

 ■ deeply forked, contained about twice in the wing. Feet stout, of moderate length ; 

 tarsi usually about two-thirds the bill ; as long as, or somewhat exceeding, the middle 

 toe and claw. Hallux exceedingly short. Webs moderately broad, quite deeply incised, 

 especially the inner one. Of variable size, from the largest of the subfamily to quite 

 moderate. General form always more or less robust. A decided occij)ital crest. Under 

 parts always white. Feet black. 



The essential characters of the subgenus, as compared with Sterna proper, are found in 

 the very large size and robust form j in the depth and stoutness of the bills ; iu the 

 stouter feet ; and in the shorter tail, which is usually rather emarginate than forked, 

 and never so deeply forked as in Sterna. The pattern of coloration is different in some 

 respects, and there is a decided occipital crest. Gelochelidoii is apparently the most 

 closely allied, but this differs remarkably in the bill ; there is no occipital crest, the 

 ■wings are longer, the interdigital webs more deeply incised. 



I have been obliged, in the preceding diagnosis of this group, to define it with con- 

 siderable latitude, in consequence of the somewhat dissimilar types which I have re- 

 ferred to it. I have not, however, felt assured of the propriety of dividing it, as now 

 limited, into two or more groups, in consequence of the close connection which the dif- 

 ferent extremes of form present through intermediate species. Thus the Thalasseus 

 caspius and T. caniiaciis differ considerably in such features as shape and robustness of 

 bill, length and emargination of tail. If we examine, however, other species, such as 

 T. regins and elegans of North America, relax of Europe, &c., we shall find some charac- 

 ters of form which are different in nearly every species, as e. g., proportions of tarsus 

 and toes in regius and elegans ; and we shall moreover be able to trace gradual transi- 

 tions in every respect, from one species to another. I prefer to retain all these large 

 species under the same subgenerio designation, as they all possess strong points of sim- 

 ilarity among themselves, and recognizable discrepancies from Sterna in its restricted 

 sense. 



Thalasseus is the first distinctive name which was proposed for this group, and is the 

 one now in most general employ. It is based upon Sterna ca»pia, as are also all the other 

 synonyms quoted at the head of this article, with the exception of Actoohelidon, which 

 has Sterna cantiaca as type. 



Analysis of the jVbcft American speoies of Thalasseus. 



A. Of large size and robust form. Bill entirely bright colored, feet blaek. 

 Tail slightly forked, with little or no attenuation of the outer 

 feathers. 



a. Tail merely emarginate. Primaries concolor on both webs (with- 

 out white stripe on inner web). Bill red. Largest : Wing 

 about 16 inches ; tail only 5 to 6 ; bill nearly 3 caspia. 



