2706 THE BONY FISHES AND GANOIDS 



large size of the slime cavities on the sides and top of the head; the ruffes being 

 specially distinguished by the dorsal fin being undivided, and also by the maxilla 

 being covered by the preorbital bone. The fishes of this genus have the body 

 somewhat low, and the scales somewhat small; the continuous single dorsal fin 

 carrying from thirteen to twenty-nine spines, and there being two spines in the anal 

 fin. There are no tusks among the small teeth of the jaws, and the tongue and 

 palatine bones are devoid of teeth, although these are present on the vomer. The 

 genus is confined to the cooler portions of the ITorthern Hemisphere, the common 

 species ranging from Britain through Central Europe to Siberia. The "pope," as 

 the ruffe is frequently called in England, is common in most of the rivers and canals 

 of that country, generally preferring slow, shaded streams, with a gravelly bottom, 

 and closely resembling the perch in its mode of life. 



Here may be mentioned a small family, with ten genera of perch- 

 imi y J"H like fishes, distinguished from the Percida and the following family by 

 the mode of attachment of the ribs, which, with the exception of 

 the last, or last two or four, are inserted on the bodies of the vertebrae behind the 

 transverse process, instead of the process itself; all the vertebrae in front of the 

 tail, save the first two or three, having such processes. Externally, these fishes 

 differ from the perches in the presence of at least three spines in the anal fin. 

 The family is typified by the North- American genus Centrachus, of which there 

 is but a single species. All are carnivorous fresh-water fishes, sometimes entering 

 estuaries, and many are in the habit of building nests for the protection of their 

 young. 



BASS AND SKA PERCHES Family SERRANID^E 



Although usually included in the Percida, with which they agree in the struc- 

 ture and relations of the vertebras and ribs, the sea perches and their allies are re- 

 garded by Mr. Boulenger as representing a family by themselves, on account of the 

 circumstance that the second suborbital bone develops an internal plate for the sup- 

 port of the eye. The number of spines in the anal fin is variable, and in one genus 

 (Centrogenys) the lower pharyngeal bones are united. The family is a very exten- 

 sive one, and may be divided into several subfamily groups. 



Together with the sea perches, the bass represent a subfamily (Ser- 

 can Perch ranin(S } presenting the following characteristics: The upper jaw- 

 and Bass Done or maxilla is exposed, its upper border not being entirely con- 

 cealed by the overlapping preorbital; the scales are not shed; there is 

 no scaly process at the bases of the pelvic fins; the anal fin has three spines; the 

 gill membrane is free behind, and tjie false gills are well developed. In distribu- 

 tion the subfamily is cosmopolitan, and while most of the forms are marine, a 

 few inhabit fresh water. Among the latter may be mentioned the South- American 

 perch {Perdchthys) of Chili, Western Argentina, and Patagonia, which, in common 

 with five other genera, has a divided dorsal fin. From an ordinary perch these fish 

 may be distinguished by the scaly upper surface of the head, and the presence of 



