LARUS ARGENT ATUS, HERRING GULL. 623 



detailed heigbteninjij the probability of the varietal distinction of L. sm'ithsonianus. 

 The Herring Gulls of both continents differ from snch species as (jlancus, hiicoptenis, 

 &c., in not being truly boreal birds. They migrate northward only to breed, and re- 

 turn south as soon as the duties of incubation are accomplished. The American spe- 

 cies, at least, rarely i)asses beyond Labrador, and is more abundant in its southern 

 than its northern portions. It is well known that the nearer to either pole is the 

 habitat of a species the more likely it is to range indiscriminately on both hemis- 

 pheres; and, conversely, the more tropical a species the more likely it is, cacteris i)ari- 

 hiis, to be specifically distinct from its transoceanic representative. We can see here a 

 reason why smithsoniamts may be somewhat dift'erent, while L. ylaucus, leucopteriis, and 

 P. ehurnea are identical. This fact is adduced merely to show why we may expect to 

 find the differences which do exist in var. smithsonianus and are absent in {/laucus ; 

 though, at the same time, I separate the variety u]nin its physical characters alone, 

 irrespective of any preconceived theory of geographical distribution. 



Synonymy. — Laroidcn argentaloides, Brehm, appears to include both the European and 

 American bird. His amerkanns indicates a bird snialler and less robust than European 

 avfjentatus, and may be consequently inapplicable here. It corresponds more nearly 

 with ^^ californtcns." The argintatoides of Bonaparte's Synopsis, represented as commoa 

 along the Atlantic coast, may really lefer to delcnvarensts. L. affinis of Reinhardt, of 

 Greenland, I have not been able to identify. 



Anatomical charactirs. — The month, in capacity, is intermediate between that of iSfe?'- 

 corarius and of Sterna ; the angle of divergence of the mandibular rami being less than 

 in the former, but greater than in the latter. The palate is quite flat both transversely 

 and longitudinally, being not at all vaulted and scarcely concave, except toward the 

 tip of the bill, where it curves downward with a considerable degree of convexity. 

 The palate is soft and vascular to within about an inch of the tip, where it becomes 

 corneous and divided by five or six longitudinal stria». At the commencement of the 

 more vascular ])art of the palate there begins a median elevation, quite broad and 

 without a central ridge, which continues back for more than two inches. This is 

 everywhere beset with stout, reversed papilhe, the largest of which are along the me- 

 dian line. The central elevation is bifurcated for nearly its posterior half, to form the 

 opening of the posterior nares, the edges of which fissure are thickly papillate, as are 

 the posterior extremities of the elevation itself. This median longitudinal prominence 

 is separated on each side by a deep sulcus from a lateral ridge. This lateral ridge an- 

 teriorlj' sinks insensibly into the common level of the palate ; posteriorly it rises up 

 very broad and thick, and, together with its extremity, is papillate. Just external to 

 these ridges are the deep depressions in which the tomia of the lower mandible are 

 received. 



Posterior to that portion of the jialate just described, there is a large, vaulted, sub- 

 triangular space, extending quite to the extremity of the palate. This space is 

 bounded anteriorly by the termination of the central median elevation already de- 

 scribed ; laterally hy the continuation backward of the lateral ridges ; more posteriorly, 

 where the sides of the triangle come together to form the apex, by a very perfect 

 fringe formed by a single thick-set row of slender, acute papilla-, placed obliquely, 

 their posterior extremities divaricating, their anterior meeting on the median line. 

 The place thus inclosed is quite smooth, being free from sulci or ruga', and presents the 

 orifice of the Eustachian tube. It is fissured along the median line by the posterior 

 continuation of the nasal aperture. The edges of the fissure cannot be accurately co- 

 aptated, as can that portion of it more anterior, the portion of the ])osterior nares con- 

 sequently remaining always more or less patent. The edges of the opening terminate 

 each in a soft papilla. On separating them, the vomer is seen nearly for its whole 

 length, dividing the na.sal aperture into a right and left. Posterior to the termination 

 of tlie nasal fissure is the usual median, longitudinally oval foramen, the o]iening of 

 the Eustachian tube ; measuring in this species a full fi)urth of an inch. All around 

 this central smooth portion the mucous membrane of the mouth is thrown up into 

 more or less irregular rugie, mostly longitudinal, and continuous with the ordinary 

 a'sopliageal folds. 



Tlu^ floor of the mouth is of a very regularly triangular shape, the sides being 

 scarcely at all concave. The rising up of the tomia of the mandible on either side gives 

 it a very considerable depth and almost per]»endicular sides, especially anteriorly. The 

 muscular and other layers coin]M)sing the lloor, are very distensible and elastic. The 

 mucous m<nii)raiie, in its undilatcd condition, is everywhere thrown up into rugie, 

 chiefly longitudinal, except just over the larynx. The muscular layers are well 

 marked, but jiresent nothing peculiar either in shape or distribution. The tongue is 

 just two inches long. It is stout and fleshy almost to the tip, wiiich is obtuse, flat- 

 tened, sliglitly bifid. Its (husiim is longitudinally channeled ; its under surface trans- 

 ver.s«'ly convex ; its posterior extremity i>rolongcd into two slwut, ol)tuse c»)rnua, whiidi 

 are tliii'kly p.-ipillate. The trianguljir, smooth emiufuce which is boine upon the sur- 

 face of Ilir larynx, measures al>i>nt an inch in extent l»y half as much in breadth. The 

 opening of the glottis divides it longitudinally for its whole length. The rima is quite 



