5B8 
PROCEEDINGS OF THE ACADEMY OF 
Habitat. — In America, the interior of the Fur Countries; Hudson’s Bay; 
Labrador ; in winter ranging southward along the Atlantic Coast as far as New 
Jersey. 
This species in all its stages of plumage is too well known to require any 
further description. 
Quite a large series of American skins, of all ages, compared with two fully 
adult birds from Europe, constantly differ in size and proportion, as shown by 
the following measurements: 
Comparative measurements of American and European Birds. 
American. European. 
Length of bill along culmen 2-75* 2-40 
“ “ “ gape 4-00 3-55 
•Height “ at base 0-90 0-75 
Width “ opposite nostrils 0-50 0-50 
Length of wing from flexure 16-50 15-00 
“ “ tarsus..... 1-75 1-65 
“ u middle toe and claw 1-65 1-55 
I “ tail 5 75 5-25 
The above measurements indicate the average of the specimens from both 
countries before me, from which it will be seen that the American bird is de- 
cidedly the larger. While the bill is nearly' a third of an inch longer, it is also 
especially remarkable for its great comparative height at the base, and its width 
at base being no greater than in the European bird, gives it quite a different 
shape. The next most patent difference lies in the length of wing from the 
flexure, in which the American bird surpasses the European by fully inches. 
Specimens of both, of course, differ among themselves to a degree; but the 
greatest variation in adult American skins is hardly half an inch. The wing 
of the adult European bird, indeed, hard'y equals that of a young bird of the 
year from America ; and it is well known how much smaller are the young of 
all Terns than the adults. The tarsi and toes of the two, as well as the tail, 
differ in a considerable degree, but not so markedly as do the bill and wings. 
I find no differences whatever in the color of the two birds. 
With but two specimens of the European bird before me, I do not venture to 
formally separate from it its North American representative. But should these 
examples prove to represent fairly the characters of the European bird, and the 
discrepancies in size and proportion above pointed out prove constant, I should 
not hesitate to do so. In that event I would propose for our bird — in the ab- 
sence of any very peculiar characters on which to base a name, and in view of 
the fact that it is the largest and most magnificent Tern of our continent — the 
name of Thalasseus imperator. 
The following would be its diagnosis: 
Th. Thalasseo caspio coloribus similis ; sed omnino major, rostro etiam vali- 
diore, locgiore, altiore nec latiore. Rostr. long. 2-75 poll.; alse 16-50. 
The proper specific appellation of the Caspian Tern is not u caspia Pallas,” 
but “ tschegrava Lepechin,” which latter name is proposed in the same work in 
which Pallas calls the bird “ caspiaf but has priority by several pages. As, 
however, the word is not only barbarous, but also exceedingly cacophonous, 
and especially as caspia has become so well established by common consent, I 
do not think it would be expedient to supersede Pallas’ name, in view of the 
very slight priority of that of Lepechin. 
Thalasseus regius Gambel. 
Sterna cayana ) Bon., 1828; Nutt., 1834; Aud., 1839 and 1844; but not of 
Latham. 
* Inches and hundredths. 
[Dec. 
