BRITISH FRESH-WATEE FISH. 51 



fin, the rays are enumerated with a line between them, 



thus — 



D. 9-12 : 



the first numeral having reference to the first, or more 

 forward, fin. 



In the Acanthopterygii with two dorsals, as in the 

 Perch, the first is usually wholly spinous, and this is indi- 

 cated, as in the last case, by a line between the two num- 

 bers; when, however, there is but one dorsal, of which 

 the fore part only is spinous, the sign 4- is placed between 

 the spinous and the soft rays. This is also the rule in 

 regard to other fins partly spiny and partly soft : thus — 



(Fin-pays of Perch) D. 15-1 + 13 : P. 14: V. 1 + 5: A. 2+8: C.17. 



Some of the soft-finned fish have an occasional spinous 

 ray; and when this is the case their position, &c. should be 

 fully described — a perpendicular line after such spinous 

 ray being drawn in the ray-formulary. Take the fin-rays 

 of the common Carp for example, — 



D. 4 I 19 : P. 17 • V. 9 : A. 3 I 5 : 0. 19. 



In this instance the 4th dorsal and 3rd anal fin rays are 

 spinous. 



The form of the gill- covers has been mentioned as one 

 of the points to be most relied on, more particularly in 

 the Salmon family, for distinguishing one species from 

 another ; for whilst, owing to circumstances of food, water, 

 or climate, different individuals of the same species will 

 often differ widely from each other, and from their original 



d2 



