30 



on posterior margin of opei'cular Hap, if present, always blend- 

 ing with the adjacent paler or darker color, and not forming a 

 definitely localized spot as in Eupomofis. 



A somewhat heterogeneous group, represented in this state 

 by eight species, the genus as here understood including Aponiofis 

 and Lqjoiiiis of recent authors. The form of the liody is vari- 

 ously elongate, elliptical, or short and deep. Most of the spe- 

 cies are inclined to be rather robust, while others are thin and 

 compressed. Mouth various, usually rather large; supplemental 

 maxillary bone well developed in some ^species, rudimentary or 

 wanting in others, its development greatest in those species 

 which have the mouth largest; teeth on palatines in most spe- 

 cies. Operculum ending behind in a convex bony or osseo- 

 membranous process or flap, its development much greater in 

 some species than in others and subject to variation with age; 

 the flap proper well differentiated (or not) from a fleshy or mem- 

 branous margin partly or wholly of paler color than the oper- 

 cular spot. Gill-rakers well developed (long, stiff, and rough ) to 

 rather slender, or very soft and weak. Pectorals nearly always 

 considerably shorter than head, but about equaling it in some 

 species [iiiiydlofis, Jmiiii/is, jxd/idus); dorsal spines usually low, 

 but scarcely lower in some species than in Eupoiuofis. 



KEY TO THE SPECIES OF THE GENUS LEPOMIS FOUND IN ILLINOIS. 



A. Operculum more or less stiffened posteriorly, its osseous 

 portion always distinctly differentiated from a posterior 

 fleshy or membranous margin, which is about equally 

 broad above, behind, and below, and partly orwholly of 

 paler color than the osseous portion, to which the Idack 

 of the opercular spot is entirely or for the most part 

 conhned. A well-developed supplemental maxillary 

 bone. 

 b. Scales moderate or small, 42 to 50 in lateral line ; oper- 

 culum produced backward and rather sharply rounded 

 behind, triangular. 



