542 
PROCEEDINGS OP THE ACADEMY OF 
Th. acuftavidus. — White margins of inner web of three or four outer prima- 
ries narrow, falling short of tip, which is wholly occupied by the black portion. 
Breadth of white margin 1J inches from tip of first primary, -10 of an inch. 
Genus STERNA Linnaeus. 
Sterna , Linn., Syst. Nat. 1748. Type, S. hirundo , Linn. 
Thalassea , Kaup, Sk. Ent. Eur. Theirw. 1829, p. 97. Type, S. paradisea, Briin. 
Hydrocecropis , Boie, Isis, 1844, p. 178. Type, ? (includes S. paradisea.) 
Slei'nula , Boie, Isis, 1822, 563. Type, S. minuta , Linn. 
Oh. — H ead without a decided occipital crest, but the feathers of the parts 
somewhat elongated; size moderate, or very small; general form slender and 
graceful. Bill about as long as, or slightly shorter than, the head, greatly ex- 
ceeding the tarsus ; of varying stoutness, but usually quite slender, very acute, 
the culmen gently curved, being slightly declinato-convex. Commissure gently 
curved ; outline of rami a little concave, of gonys quite straight, the angle at 
symphysis well marked and acute, but not very prominent. Wings long and 
pointed. Tail of variable length *and amount of f'orfication, but always de- 
cidedly greatly forked ; the lateral feathers elongated, slender and tapering, 
greatly surpassing the others. Tail contained in the wing of the type of the 
genus about If times; in arctica 1J times; while the tail of paradisea is but 
little less than the wing. Tarsus slender, slightly shorter than the middle 
toe and claw, slightly longer than the middle toe alone ; much shorter than 
the bill, about equal to the distance between the projection at symphysis and the 
tip of the inferior mandible. 
The genus Sterna , in the restricted acceptation in which it is employed by 
most modern authors, embraces quite numerous species, all more or less inti- 
mately related to S. hirundo. The group is one well defined, its species agree- 
ing very closely in size, general form, pattern of coloration, and seasonal 
changes of plumage. Specific characters are generally found in the varying 
length and stoutness of bills and tarsi, amount of forking of the tail, markings 
of the primaries, and other less decided features of coloration. 
Sterna proper has comparatively few synonyms, the principal of which are 
those given at the head of this article. Thalassea , Kaup, and Hydrocecropis , 
Boie, are strictly synonymous, while Sternula , Boie, is based upon a species 
differing but very slightly from the type, S. hirundo. 
u Sterna Trudeaui Aud.” 
Sterna Trudeaui , Audubon, Orn. Biog. v. 1839, 125. Law?. Gen. Rep. Birds, 
1858,861. 
I have before me a typical specimen of Sterna Trudeaui , belonging to J. P. 
Giraud, Jr., the one from which was drawn up the description in the General 
Report, and supposed to be also the original of Audubon’s plate and descrip- 
tion. As these are the chief descriptions of the bird which have ever appeared, 
and as, I believe, the specimen is the only one known to exist, it may fairly be 
considered to embody all that is at present known of the species. From the 
peculiar characters presented by it, as well as by the species which succeeds, 
— to both of which attach, for various obvious reasons, doubts as to validity, 
— it may be of advantage to examine somewhat closely into its charac- 
ters, to determine if possible whether they be distinct from each other ; and in 
that case in what they differ from S. Forsteri. 
The bill is quite stout at the base, both as regards height and width, and 
tapers regularly to an acute point, the culmen being but slightly arcuate. It is 
precisely the length of that of an adult Forsteri, and also of a supposed TIavelli .* 
* The specimens of “ Havelli ” referred to, are those furnished by Mr. Lawrence, and so labelled 
by him. 
