HISTORY OF THE AMERICAN MENHADEN. 35 



bead, where it expands iuto a globular pear-shaped muscnlar organ 

 with thick walls, which have their inner surfaces rugose, like those of 

 the gizzard of a gallinaceous bird. At the anterior end of the stomach 

 is a mass of fine, hlil'orm, pyloric appendages, surrounding the origin of 

 the intestine, which is very long and is arranged in two coils, one upon 

 each side of the stomach, enveloping it completely. The length of the 

 intestine is live or six times that of the whole iish. 



The sicim-hladder. 



54. The swim-bladder is small and inconspicuous. Its walls are thin. 

 It is not probable that it contains enough gelatine to be of commercial 

 importance. Hyrtl was unable to detect its presence in the fish studied 

 by him as Clupanodon aureus, but which was probably something very 

 diHerent. 



III.— GEOGRAPHICAL DISTEIBUTION AND MOVEMENTS. 



11. — GEOGRAPHICAL RANGE. 



Limits in 1877. 



55. It is not easy to define exactly the boundaries of geographical 

 range for any species, unless they be marked by some impassable bound- 

 ary. It is especially difficult in the case of fishes. The limits of their 

 wanderings appear to depend directly or indirectly upon temi^erature, 

 and to vary considerably, from season to season, with the seasonal vari- 

 ations in the mean temperature of the water. 



As nearly as it can conveniently be expressed the range of the north- 

 ern menha(\en, Brevoortia tyrannus, is as follows: it is to be found at 

 some j)eriod during the year in the coastal waters of all the Atlantic 

 States from Maine to Florida (approximately between the parallels of 

 north latitude 25° and 450)5 on the continental side it is limited approxi- 

 mately by the line of brackish water; on the ocean side, by the inner 

 boundary of the Gulf Stream. What may be the limits of its winter 

 migrations it is impossible to say. A surface temperature of about 51° 

 is necessary for its appearance in waters near the shores. 



Variations of the northern limit in the past. 



56. Its northern limit of migration seems to have always been the 

 Lay of Fundy. Perlcy, writing in 1852, stated that they were sometimes 

 caught in considerable numbers in weirs within the harbor of Saint 

 John's, N. B.* 



^Descriptive Catalogno (in part) of the fishes of New Brunswick and Nova Scotia, 

 by M. II. Perloy, esq., Her Majesty's emigration officer at St. John's, New Brunswick. 

 (Second edition.) Fredericton : J. Simpson, Printer to the Queen's Most Excellent 

 Majesty, 1852, p. 30. 



