;28 MARKETABLE BRITISH MARINE FISHES 



feature in the larva is the mantle of black star-shaped pig- 

 ment specks in the roof of the belly cavity : the larva being 

 transparent, this pigment is very conspicuous. There are also 

 yellow pigment and a few black specks on the head and yolk-sac, 

 but at first there is none in the tail. 



The Gurnards (^Trigla gunmrdits, cuculus, Jiinindo and lyra). 



The differences among these fishes in importance and in 

 history are so slight that nothing would be gained by giving a 

 separate account of each. 



DistingnisJiing Characters. — It should be understood that the 

 bones which cover the surface of the head are the same which are 

 present in the heads of other fishes, but here are thicker and broader, 

 and bare, no soft skin extending over them. The bones of the gill- 

 cover are furnished v/ith strong spines. The three separate rays 

 of the breast fins which form one of the most remarkable pe- 

 culiarities of these fishes remind one somewhat of the legs of an 

 insect, but are more properly to be compared to our own fingers, 

 since they are part of the divided extremity of limbs which 

 correspond to our own arms. Their use, too, is more that of 

 fingers than of legs, since they are employed, like the barbels of 

 other fishes, to feel the ground and rake over loose stones, in 

 order to discover small Crustacea and other animals on which the 

 fish feeds. These fishes have another interesting peculiarit}- : 

 they utter sounds, resembling faint grunts. These sounds are 

 produced in the air-bladder. That organ is entireh- closed, and 

 its walls contain well developed muscles, which b}- their contrac- 

 tion, drive the air from one part of the bladder to another. In the 

 tub, or latchet, the air-bladder consists of three portions, a larger 

 central chamber and a smaller chamber on each side, communi- 

 cating with the central chamber at the front end. At the hinder 

 portion of the central chamber there is a partition running in a 

 slanting direction across it, and in the middle of this partition is 

 a round opening. The air is pressed to and fro through this 

 opening, and so the sound is produced. 



The use of the sounds is not well understood, no thorough 

 investigation of the question b}' means of experiments and obser- 

 vations on living fish in aquaria having yet been made. But it 



