STERNIN^, TERNS. 663 



Analysis of the North American forms of Sterninai. 



A. Nostrils sub-basal. Frontal antize 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 Stekke.®. 



a. Webs moderately indeed. Tail well formed, generally 

 more than half as long as the wing. Under parts 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 GeloelieUdon. 



•X. 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, 

 deeply forked. Size medium and small.. Stebna. 



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



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



cent Haliplana. 



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

 Tail merely emargiuate, hardly or not half as long as 

 the wing. Under parts in summer black Hydeocheltdon. 



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



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

 Tarsi very short. Toes lengthened, the lateral nearly as long 



as the middle, with fuU webs Group Axoe^. 



Color fuliginous Anous. 



Subgenus Gblochelidon, Brehm. 



<^Sterna, Mont., Orn. Diet. Suppl. 1813. (5. anglica.) 



X Thalasseus, BoiB, Isis, 1823, 563 (not type). 



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



= Gelochelidon, Bkehji, Naturg. Vcig. Deutscli. 1831, p. — . (S. angliea.) 



=Laropis, Wagl., Isis, 1832, 1225. (S. angliea.) 



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

 pressed ; the culmen nearly straight to beyond the nostrils, then very declinato-couvex 

 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 short and broad, not deep ; nostrils short, widely oval, placed 

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

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

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

 tained 2^ times in tlie wing from the carpus ; deeply eniarginate, but its lateral feathers 

 not elongated nor attenuated. Feet long and stout for this subfamily. Tarsus shorter 

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

 being unusually long for this subfamily ; inner shorter than outer ; interdigital mem- 

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

 inch. Claws slender, slightly arched, acute. Scutella as in Sterninw generally. Size 

 moderate. Tail and ramp concolor with the back. Anatomical characters those of 

 Sterninw generally. 



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

 and obtuse bill, though other characters may be noted. The bill not distantly resembles 

 that of Larinoe, and the group may be looked upon as thu connecting link between the 

 two subfamilies. It differs in pattern of coloration from most other Terns, in having 

 the color of the mantle continued uninterrnptedly on to the tail. Anatomical differ- 

 ences between it and Sterna proper are hardly to be appreciated, excei)t, of course, 

 those characters of the bones upon which the proportions of the bill and feet depend. 



Of the several accredited species supposed to compose the genus. North America 

 possesses but one, which is identical with that of Europe. 



The genus has but few synonyms, the species comprised in it having been ordinarily 

 referred to Sterna. Wagler's synonym {LarSpis) is antedated by Gelochelidon of Brehm, 

 which latter is the first distinctive name. 



