STERNIN.E, TERNS. 



663 



Analysis of the North American forms of Sterniua: 



A. Nostrils sub-basal. Frontal antioa prominent, embracing base of 



culmen. Tail more or less forked. Tarsus not shorter than 

 middle toe without the claw. Lateral toes much shorter than 



the middle. Webs excised Group Sterner. 



a. Webs moderately incieed. Tail well formed, generally 

 more than half as long as the wing. Under jjarts white 

 or light. 



a'. Upper parts pearl-gray. Cap in summer black, or 

 a black bar through eye. 



1. Bill short and very stout, somewhat gull- 



like, black. Tarsi much longer than the 

 toes, black. Tail lightly forked. Medium 

 size Gelochelidon. 



2. Bill long, large, bright colored, or with yel- 



low tip. An occipital crest. Feet black. 



Forking of tail variable. Of large size.. Thalasseus. 



3. Bill moderate, slender, usually bright col- 



ored, like the feet. No crest. Tail long, 



deejily forked. Size medium and small.. Sterxa. 



h'. Upper parts dusky. Cap like the back. 



4. Bill and feet black. A white frontal cres- 



cent JHaliplana. 



i. Webs deeply incised (feet little more than seraipalmate). 

 Tail merely emarginate, hardly or not half as long as 

 the wing. Under parts in summer black Hydrochelidon. 



B. Nostrils nearly median. No frontal antise, the feathers extending 



further on culmen than at the sides. Tail double-rounded. 

 Tarsi very short. Toes lengthened, the lateral uearlj' as long 



as the middle, with full webs Group Anoe.*:. 



Color fuliginous Angus. 



Subgenus Gelochelidon, Brehm. 



<^Sterna, Mont., Orn. Diet. Suppl. 1813. (S. anglica.) 



X Thalasseus, BoiE, Isis, 18'22, 5(J3 (not type). 



X Viralva, Steph., Gen. Zool. xiii, 1826, 174 (not of Leach). 



= Gelochelidon, Brehm, Naturg. Vog. Deutsch. 1831, p. — . {S. anglica.) 



=^Laropis, Wage., Isis, 1832, 1225. {S. anglica.) 



Char. Bill rather shorter than the head, exceedingly robnst, not very acute, com- 

 pressed ; the culmen nearly straight to beyond tlie nostrils, then very decliuato-convex 

 to the tip, rather broad and rounded for its whole length ; the gonys about straight; 

 rami slightly concave; symphyseal eminence well marked; tomia of lower mandible 

 inflected ; commissure gently curved. Height of bill at base, a third of total length. 

 Nasal groove exceedingly shoit and broad, not deep ; nostrils short, widely oval, ])laced 

 very near the base of the bill, just beyond the terniiuatioii of the feathers. Wings 

 exceedingly long and acute, each primary suri»assiug the next by a full inch ; the sec- 

 ondaries short, .soft, obliquely incurved at their extremities. Tail rather short, con- 

 tained 2i times in the wing from the carpus ; deeply eniaiginate. but its lateral feathers 

 not elongated nor acienuated. Feet long and stout for tliis subfamily. Tarsus shorter 

 thau the bill, longer than the middle toe and claw. Hind toe remarkably developed, 

 being unusually long for this subfamily ; inner .shoitcr than outer ; iiiterdigital mem- 

 branes moderately broad, deeply incised, especially the inner. Tibia naked for half an 

 inch. Claws slender, slightly arched, acute. Scntella as in Sternina' generally. Size 

 ino<lerate. Tail and rump concolor with the back. Anatomical characters those of 

 Sternituv generally. 



The above diagnosis is of a group which differs chiefly from other Sttruina', in the robust 

 and obtuse bill, tlioiigb other diaiacters may he noted. The bill not distantly resembles 

 that of Larhuf, and the giouii may be looked u]iom as the connecting link between the 

 two subfamilies. It diflcrs in i)attern of coloration from most other Terns, in having 

 the color of the mai:tle continued uiiiiiternii)t(dly on to tln^ tail. Anatoniieal dili'ei- 

 ences between it and Stcrua proper are hanlly to be api)reciated. except, of course, 

 those characters of the bones upon which the proportions of the bill and feet dt-pend. 



Of the several accredited species su]ij)ose(l to compose the genus, North America 

 possesses but one, which is idtntlcal witli that of Europe. 



The genus has but lew .syiKuiyiiis, the species comprised in it having been ordinarily 

 referred to Stcniii. Wagler's synonym (I.anqii'^) is antedateil i»y Gdorhclidoii ot Brehm, 

 which latter is the lirst distinctive uume. 



