566 Allis Shad 
come close together, forming a complete sieve. If reference be made 
to the illustration one has a better idea of this beautiful construction 
(Fig. 235). 
There is yet another shad, known as the twait shad, which can be 
identified from the allis shad by its having six to eight spots on its 
sides, whilst the former has only one behind the gills. In addition 
to the shads, the smelt and sturgeon invade our fresh waters. 

