117 
AL08A. 
This geniia 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 ^1 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 Clupeas, or Herring family, the separation 
of the lobes is particularly conspicuous; and in the genus Alo&a 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. DAMIN HEREING. 
Shad, 
Clupea aloea, 
Alosa vulgaris, 
WiiiOTJGHBY; Plate p. 3, f, 2, Agon'e, and p. 
227, but he confounds this species with 
A. finta, the Twait Shad; as do many 
others. 
CuviEB. Jenyns; Manual, p. 438. 
Yarbell; Br. Pishes, 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 Greeks and Homans, 
