I. '08. 12 



convenient situation which have proved such important factors 

 in the success of the Norwegian fishery. 



Natantia form a valuable source of food supply to many 

 marketable fish. In their early free-swimming stages they are 

 consumed by Herring and Spring Mackerel, but do not, of 

 course, constitute such an important item in their dietary as 

 the ubiquitous Copepod. Certain forms, principally the more 

 abundant species of Cranyon and Pandalus seem to be esteemed 

 above all other food by such fish as the grey gurnard, while, 

 along with other Crustacea, they are freely eaten by many 

 valuable species of Gadoids (more especially by the Haddock) 

 and by Rays and Skate. 



Adult flat fish do not seem to partake of Natantia to any 

 great extent, they are none the less of some importance to 

 certain species, notably the Long Eough Dab. 



Leander is a favourite food of the Bass, and is doubtless 

 eaten largely by other fish frequenting rocky localities near 

 the shore. 



DECAPODA NATANTIA. 



Teibe PENAEIDEA. 



The two families may be separated thus : — 



I. Last two pairs of pereiopods well 



developed; branchiae numerous, Penaeidae. 



II. Last two pairs of pereiopods reduced 



in size ; branchiae not more than 

 eight on either side, sometimes 

 absent, .... Sergestidae (p. 24). 



Family PENAEIDAE. 



Of this family three genera have been recorded from British 

 and Irish waters, but the presence of one of them requires 

 confirmation. 



I. Inner border of first segment of 

 antennular peduncle bearing a 

 twisted setose scale, forming an 

 incomplete inner wall to the orbit ; 

 second joint of mandibular palp 

 longer than first ; second maxilli- 

 pedes not foliaceous ; rostrum well 

 developed, with numerous dors,al 

 teeth. 



A . Antennular flagella cylindrical ; 

 one arthrobranch but no epi- 

 pod on fourth pair of pereio- 

 pods, .... Pen<ieus fp. 13). 



