G66 STERNA ANGLICA, GULL-BILLED TEEN. 



eau. I have been unable to detect any discrepancies, nor do I think that any charac- 

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

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

 uauie, lioAvever, has been generally adopted for our bird since the time of its use iu that 

 connection by Bonaparte, iu 18'.)8. 



Sy 110 III/ til I/. — The name aufjUca is rather an unfortunate one, since the bird, though 

 then described from specimens shot iu 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 

 Macgiilivray. 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 iu 

 so doing. 



Subgenus Thalasseus, Bote. 



<^ Sterna, Pall., Nov. Comm. Petrop. siv. 



< Thah(Sf<ciis, Boie, Isis, 1822, 5G3 (type S. caspia, Pall.).— Coues, Rev. Sterninw N. A. 



Pr. A. N. S. Phila. Dec. 1862,'5:56. 

 ^ Hydroprogne, Kaup, Sk. En't. Eur. Thierw. 1829, 91. {S. caspta.) 



> SyloclidMon, Brehm, Viig. Deutsch. 1831, 770. (S. caspia.) , 



^ HcJojms, Wagl., Isis, 1832, l;i2}. {S. caspia.) 

 y- Actochelidon, Kaup, Sk. Ent. Eur, Thierw. 1829, 31. (Sterna eantiaca.) 



Gen. char. 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. Cnlmen variable in amount of curva- 

 ture, from uearly straight to very convex. Gonys of variable length. Wings ouly 

 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 A^ery 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 iu 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 inuer one. Of variable size, from the largest of the subfamily to quite 

 moderate. General form always more or less robust. A decided occipital crest. Under 

 parts always white. Feet black. 



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

 the very large size and robust form ; 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. Geloelielidon is apparently the most 

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

 wings are longer, the intcrdigital webs more deeply incised. 



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

 siderable latitude, in cont-equence 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 preseut through intermediate species. Thus the lltalasseus 

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

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

 T. reyius and elcyans of North America, vclox of Europe, &c., we shall find some charac- 

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

 and toes in reyhts aud eleyatis ; and we shall moreover be able to trace gradiuil transi- 

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

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

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

 sense. 



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

 one now in most general employ. It is based upon Sleriia caspia, as are also all the other 

 synonyms quoted at the head of this article, with the excejttion of Actochelidon, which 

 has Sterna eantiaca as type. 



Analysis vf the Xorth American species of Thalasseus. 



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

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

 feathers. 



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

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



about IG inches ; tail only 5 to (i ; bill uearly 3 citsjyia. 



