50 



THE FRESH-WATER FISHES OF EUROl'K. 



Cottus gobio (CUVIER). The Miller's Thumb, 



1 D. 89, 2 D. 1518, A. 1213, P. 1314, V. 1/4, C. 13. 



The head in the River Bullhead, or Miller's Thumb (Fig. 18), is the 

 broadest part of the animal, and is widest in the region of the gill-opening. 

 It is nearly always as broad, or broader, than long, though its breadth 

 differs with the form of the operculum. The length of the head is usually 

 equal to one-fourth the entire length of the fish. The deepest part of the 

 body below the first dorsal fin is equal to one-fifth of the total length, but at 



Fig. 18. coTTt'S GOBIO (CUVIER). 



the caudal fin the height of the body is only one-twelfth or one-thirteenth 

 of its length. Behind the head the body is compressed from side to side in 

 a wedge shape to the tail. The eyes are superior (Fig. 19), but directed 

 obliquely outward, are nearer to the snout than the gill-opening, and are 

 small, having a diameter of less than one-fifth of the length of the head. 



The profile of the fore part of the head is a segment 

 of a circle ; both jaws are equal, and the pre-maxillary 

 and mandible, as well as the vomer, possess broad 

 bands of villiform teeth. The cleft of the mouth 

 generally reaches back beneath the middle of the 

 eye. The pre-operculum is armed with a spine di- 

 rected upward, and a much smaller spine beneath it 

 hidden in the skin. The operculum ends behind 



in a rounded point; the sub-operculum has a short sharp spine directed for- 

 ward, but generally covered with skin. The gill-opening is moderately large, 

 the number of branchiostegal rays is six, the accessory gills are large and 



Fig. 19. HEAD OF COTTVS 



GOBIO, SEEN FHOM THE 

 FRONT. 



