116 ORDER ACANTHOPTERYGII. 



head, and by having small spines without denticula- 

 tions on the operculum and preoperculum, 

 There are two in the fresh waters of Europe. 



Perca cernua, Lin. Bl. 53. 2., Cuv. and Val. iii. pi. xli. 



Is a small fish of good flavour, found in all our fresh 

 waters ; rather olive, spotted with brown. 



Perca Schraitzer, L. Bl. 332. 



Is found in the Danube ; is larger, and has on the 

 sides blackish interrupted lines \ 



Rypticus, Cuv. 



Have also only small spines on the operculum, and 

 their scales moreover, like those of grammistes, are 

 small, and hidden under a thick epidermis. The 

 single dorsal fin distinguishes them especially from 

 the grammistes. 



There is one in America of a blackish violet, ( an- 

 tkiassaponaceuSjJil., Sch.), Parra xxiv. 2., to which its 

 soft skin, endowed with a frothy viscosity, has given 

 the name of savonnier 2 , or soap maker. 



Polyprion, Cuv. 



Have not only denticulations on the preoperculum and 

 spines to the operculum, but there is also on the latter 

 bone a furcated crest, very sharp, and in general the 

 bones of their head have much asperity. 



1 Add Perca acerina, Guld. Nov. Com. Petrop. xix. 455. 



2 Add Rypticus arcnatus, Cuv. and Val. iii. pi. xlvi. 



