CENTRARCHID.€ — THE SUNFISHES 233 



branehiostegals 6, rarely 7 ; pseudobranchiae small, nearly or quite covered 

 by skin; gill-rakers variously formed, always armed with small teeth; 

 preopercle entire or somewhat serrate; opercle ending behind in two flat 

 points or prolonged in a black or partially black flap at the angle; mouth 

 terminal; premaxillaries protractile; maxillary typically with a supple- 

 mental bone, which is obsolescent or wanting in some small-mouthed 

 forms; teeth in villiform bands on premaxillaries, lower jaw, and vomer, 

 and usually on palatines; tongue sometimes with teeth; no canine teeth; 

 lower pharyngeal bones separate, with conic or paved teeth; intestinal 

 canal short; pyloric ca^ca 5 to 10; air-bladder without duct in adult; color- 

 ation usually brilliant; the young more slender than the adults and in 

 most species marked by broad transverse bars. 



Fresh waters of North America; genera about 12, species about 

 30. Seven genera and 13 species found in the waters of Illinois. 



This family includes the crappies and black bass in addition to the 

 smaller forms more commonly referred to under the name of "sun- 

 fishes." The species range in size from the smaller sunfishes, some 

 of which seldom exceed 3^ inches in length, to the rock bass and the 

 crappie, which reach a weight of more than 1 lb, and the black bass, 

 the large-mouth form of which occasionally weighs 12 to 14 lb. 



The typical deep-bodied sunfishes, taken together as a group of 

 species, are about equally frequent in lowland lakes, creeks, and the 

 smaller rivers, and about half as common in upland lakes and in 

 rivers of the larger size, our general coefficients being 1.13 for each 

 of the first three situations and . 6 and . 55 respectively for the last 

 twi i. 



All the family are spring spawners so far as known. Most of the 

 species build nests, which consist of holes scooped out in alluvial, 

 leafy, or sandy bottom about the margins of the waters they inhabit. 

 Sexual differences in form or coloration are not much developed. 



All except the very small species are valued as food, the sunfishes 

 and crappies being among the best of pan-fishes. The output of 

 sunfishes, not including crappie and bass, for the states of the 

 Mississippi Valley in 1899 was 910,963 lb. Of the total, 507,680 lb 

 were furnished by the Illinois River alone. 



The sunfishes proper — that is, the Centrar chides exclusive of the 

 black bass — are a well-marked and homogeneous group of species as 

 to form and external structure, but a diverse assemblage as to eco- 

 logical relationships. Some of the species, for example, prefer run- 

 ning water, and others quiet; some a clean hard bottom, and others 

 a bottom of mud; some turbid water, and others clear; some creeks 

 and rivulets, and others the larger rivers. They also form a diverse 

 group in respect to the disposition of the several species to avoid each 



