50 THE BliESH- WATER FISHES OF EURUPE. 



Cottus gobio (Ci vier).— The Miller's Thnmb. 



1 D. 8—9, 2 D. 15—18, A. 12—13, P. 13—14, 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 i-eg-ion 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 lish. The deepest part of the 

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



Fig. 18. — coTTUs Goino (cuviek). 



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 ]H-e-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 branehiostegal rays is six, the accessory gills are large and 



Fig. 19. HEAD 



GomO, SEEN 

 FUONT. 



)F COTTUS 

 •■ROM THE 



