572 
THE OCEAN WORLD. 
rivers the masses of shad taken in the seine-net have been so great 
that no amount of exertion has been sufficient to land them. It 
sometimes attains a very considerable size, weighing as much as from 
four to six pounds. The shad taken at sea are less delicate in their 
flesh than those caught in fresh water. The habits of the shad 
are very imperfectly known. Two species are found on the British 
coast, namely, the Twaite Shad of Yarrell (Alosa fiwta ), which is 
about fourteen inches in length, brownish green on the back, inclining 
to blue in certain lights, the rest of the body silvery white, with five 
Fig. 383. The Shad (Alosa communis). 
or six dusky spots on each side arranged longitudinally. The jaws 
are furnished with distinct teeth ; the tail deeply forked. 
The second species, the Common or Allise Shad ( C . communis), is 
considerably larger, sometimes attaining twelve and even fifteen inches 
in length, having only one spot on each side of the body near the 
head; the jaws without teeth, the scales small in proportion. This 
species is plentiful in the Severn, but rare in the Thames. 
The shad is found in the Severn and Thames in considerable 
quantities about the second week in July. They reach the fresh 
water about May, deposit their spawn, and return to salt water in 
July. Their scales are large. 
The Sprat. (0. spratus) has been the subject of a great controversy 
