Clnpeidae 



19 



the Salmonidae in most external features, but difier in the absence 

 of the adipose fin. Of our British species, the Shads differ from 

 the Herring, Sprat and Pilchard structurally in that the upper 

 jaw has a well-marked median notch, and biologically in that they 

 ascend rivers, especially the Shannon and the Severn, from April 

 to June, to spawn in fresh water. The eggs lie at the bottom of 

 the river, and the young fish migrate to the sea when they are 

 two years old and about 6 inches long. 



^^. Allis Shad, Aloui alosa. — This species is especially dis- 

 tinguished by the long and slender gill-rakers, numbering 55 to 85 

 on the lower part of the anterior branchial arch (fig. 12b). It 

 reaches a weight of 8 lbs. The specimen exhibited, 24 inches 

 long, is from the Severn at Gloucester. 





Fig. 11.— Twaitr Shad. 





B. 



Fig. 12 — Anteeior Bbanchiai, Arch of (A) Twaite Shad axd 



(B) Allis Shad. 



r, gill-rakers. 



34. Twaite Shad, Alosa finta (fig. 11).— The Twaite Shad 

 has the gill -rakers much shorter and fewer than in the Allis Shad, 

 numbering only 24 to 27 on the lower part of the anterior 

 branchial arch (fig. 12a). It attains a length of 20 inches and 



c 2 



