34 MARKETABLE BRITISH MARINE FISHES 



distinguished by their hard jointed outer covering or shell, and 

 their numerous pairs of jointed legs. The oyster represents the 

 Molluscs, of which the principal sub-tribes are the bivalves having 

 two shells hinged together like the oyster and mussel, the 

 univalves like the periwinkle or whelk, and the cuttle-fishes and 

 squids which have no external shell and are active swimmers. 

 Of Worms there are myriads of different kinds. The creatures 

 of the star-fish tribe are called Echinoderms, or spiny-skinned 

 animals, and occur in three principal forms, the rayed form like 

 the star-fish, the globular form like the sea-urchin, and the 

 cylindrical form like the sea-cucumbers. The animals represented 

 by the jelly-fish also have the radiate or star-like structure, 

 presenting a number of similar parts arranged round a centre. 

 The tribe includes besides the floating jelly-fishes, the sea- 

 anemones, which are attached by a flat base to rocks, stones, and 

 shells, and the zoophytes, which are commonly supposed to be 



Fig. I. — The Smaller Spotted Dog-fish. D.F. dorsal fin; V.F. ventral fin; C.F. 

 caudal fin; Pc. F. pectoral fin; Pv. F. pelvic fin; G. S. gill-slits; Sp. 

 spiracle ; L. L. lateral line. 



The outline figures in this chapter are Ijased upon the illustrations of Day's British 

 Fishes. 



sea-weeds and which grow from a fixed base in a branching 

 plant-like form. In addition to all these there are the sponges 

 and the minute microscopic creatures which belong to the animal 

 kingdom and are simple particles of living substance which multi- 

 ply by self-division. The plants of the sea consist of the well- 

 known sea-weeds, and a vast multitude of different kinds of 

 minute green or brown particles which are suspended freely in 

 the water. For the purpose of the present work these various 

 tribes of creatures will only be mentioned in their relation to the 

 life of fishes, and a general survey of the characteristics of the 

 principal British marine fishes is now to be given. 



Fishes then may be defined as aquatic animals which have 



