THE TWAITE SHAD 135 



numbering twenty-four to thirty on the lower part 

 of the anterior branchial arch in fish of more than 

 6 inches long. The scales are larger and more 

 regularly arranged ; I count fifty-eight to sixty-six in 

 a longitudinal and sixteen to twenty in a transverse 

 series. The specimens I have examined have twelve 

 to sixteen branched rays in the dorsal and sixteen 

 to nineteen in the anal fin, whilst the base of the 

 latter measures about one-fifth of the distance from 

 the head to the caudal fin ; the pectorals seem to 

 be somewhat shorter than in the Allis Shad. The 

 external differences between this species and the 

 preceding are shown on Plate XIX, where two fish 

 of nearly the same length, i i and 1 2 inches, are 

 figured. This species occurs on the Atlantic coasts 

 of Europe, and is represented in the Mediterranean 

 by an allied but distinct form {Clupea niloticd) ; it 

 attains a length of 20 inches and a weight of 3 J 

 to 4 lbs. 



In its habits the Twaite closely resembles the Allis 

 Shad, but is generally smaller and occurs in greater 

 numbers ; from the structure of its gill-rakers one 

 would infer that the minute crustaceans, which form 

 so large a proportion of the diet of its congener, are 

 not consumed by it to the same extent, and that it 

 is perhaps more destructive than the Allis Shad to 

 the fry of Herrings, Sand-eels, etc. 



This species usually enters fresh water later than 

 the Allis Shad, from the middle of April to the 

 beginning of June ; in the Rhine it does not ascend 

 nearly so far as its congener, but in our rivers, which 

 are much smaller, there is little to choose between 

 them in this respect. Thus the Twaite used to ascend 

 the Severn as far as Montgomeryshire, although it 



