THE BULL-HEAD 237 



Nearly all the Scorpaenoids are marine, and only 

 a small proportion of the Bull-heads occur in fresh 

 water. The genus Coitus includes a considerable 

 number of species from northern seas and rivers ; of 

 two European freshwater species one is found in 

 our islands. 



THE BULL-HEAD or MILLER'S THUMB (Cottus 

 gobid] is a scaleless fish, with the head broad, 

 depressed, and rounded in front, and the body 

 subcylindrical, tapering backwards. The mouth is 

 terminal, rather wide, with thickish lips, and with 

 small pointed teeth forming bands in the jaws and 

 across the head of the vomer. The eyes are rather 

 small and are situated in the anterior half of the 

 head and nearly on its upper surface. All the 

 bones of the head are hidden beneath the skin, 

 from which there emerges on each side a rather 

 strong, curved, backwardly directed spine, arising 

 from the praeopercle ; the gill-openings are restricted 

 by the union of the gill-membranes with the isthmus. 

 The spinous dorsal fin is short and low, composed 

 of from six to eight simple, slender, flexible rays, 

 which are unjoin ted, and are therefore regarded as 

 spines in spite of the fact that they are not strong 

 and pungent; it is followed immediately by the 

 longer and higher soft dorsal fin, formed of fifteen to 

 eighteen articulated rays which are either simple 

 or else bifurcated at the tip ; the anal fin is similar, 

 but a little shorter, of eleven to fourteen rays ; the 

 caudal has the posterior edge truncate or slightly 

 convex. The pectoral fins are large, with a broad 

 oblique base, and the pelvic fins, of a small spine 

 and three or four simple articulated rays, are inserted 

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