146 



THE FRESH-WATER FISHES OF EUROPE. 



The mouth is terminal, and the upper jaw scarcely projects beyond the 

 mandible. The diameter of the eye varies, and may be contained four and a 

 half times, or only three and a half times in the length of the head. This 

 difference is not dependent on age, but is peculiar to certain localities. An 

 eye of the same size is sometimes one diameter from the snout, and some- 

 times distant half as far again. The angle of the mouth, which is sharply 

 inclined, may reach to the front of the orbit, though it sometimes goes no 

 farther back than the nares. The inter-orbital space is equal to from one 

 to two diameters of the orbit, and is rather wider in the male than in the 



Fig. 73. LEUCiscrs KCTILUS 



female. The sub-orbital arcade is formed of four to six bones, of which two 

 are large and two small. The pharyngeal teeth are in a single row, usually 

 five on each side, though sometimes there may be six on one side, and five 

 oil the other. As in all other Cyprinoids, when a tooth is broken, the base 

 is removed, and a new tooth grows in the depression. 



The dorsal fin is situate on the convex back, nearly half-way down the 

 length of the body, and behind the origin of the ventrals ; but farther forward 

 than in the Rudd. This fin is higher than long, with the last ray half the 

 length of the longest ray, so that the slightly concave posterior border has a 

 truncate appearance. The pectoral fins are usually feebly developed, and 

 scarcely longer than the ventrals. The anal fin commences behind the last 

 ray of the dorsal ; it is less elevated, but varies, both in the length of its 

 base and of its rays. The ventrals also vary in form and length. The caudal 

 fin is deeply notched, and the lobes are pointed. The terminal rays are 

 longer than the head. 



