117 



ALOSA. 



Tins genus is distinguished from Clupea by a recess in the middle 

 of the line in front of the middle jaw ; and however slight the mark 

 by which they are separated, it is convenient as pointing out a family 

 which differs in its habits from those of the genus Clupea, as now 

 defined. 



In almost all fishes in which the tail is forked, the upper and lower 

 divisions act in some measure as separate fins, their action being often 

 in opposite directions; but in the Clupea, or Herring family, the separation 

 of the lobes is particularly conspicuous; and in the genus Alosa it is 

 still wider, the separation being marked with a difference of structure ; 

 at which part there are two peculiar fan-shaped rays, which must have 

 a different function from those above and below. At this part the 

 body is only moderately covered with scales generally; which renders 

 the structure of our scale-tailed species the more remarkable. The air- 

 bladder is long and slender, and the tube which connects it with the 

 vent is even more slight than in the Herring. 



ALLIS SHAD. 



SCADINA. ALEWIFE. BAMIN HERUING. 



Shad, Willoughby; Plate p. 3, f, 2, Agone, and p. 



227, but he confounds this species with 

 A. finta, the Twait Shad; as do many 

 others. 



Clupea alosa, Cuviee. Jenyns; Manual, p. 438. 



Alosa vulgaris, Yaeeell; Br. Fishes, vol. ii, p. 213. 



This species is widely distributed in the moderately temperate 

 regions, and in the Mediterranean appears to have attracted 

 attention at an early date; as it is noticed, under the name of 

 Thrissa, generally by the writers on Natural History among 

 the (jreeks and Romans. 



