THE AMERICAN NATURALIST. [Vol. XXXVIII. 



Central muscular thickening passir 



CLUPEID^. 



Max. V. not attached mesally Clnpea harengus 



. Max. V. attached mesally. 

 B. Attached on one perpendicular median line. 



C. Mand. V. a crescent, wide ; the distal two thirds thin and deli- 



cate, no pigment Dorosoma cepedianum 



CC. Mand. V. a horseshoe with pointed ends and the free mar- 

 gin rather squared off at the apex of the curve not 



wider at apical part of curve than on sides, (Fig. 2, s) 



Opistheoma oglitiiim 

 BB. Max. V. attached mesally on two lines. (Fig. a. b.) 



D. Attachment V-shape. (Fig. 3, a) Chipea pseiidoharengns 

 DD. Attachment in parallel lines, margin between ends of these 



lines free. (Fig. 3 ^.) Clitpea CBstivalis 



PERCAD^. 



Thickening in Max. V., a three quarters circle flattened against attach- 

 ment and covering most of width of valve . . Perca americanum 

 . No thickening. 



B. Papillae and pigment Hadropterus aspro 



BB. No pigment. 



C Boleosoma nigrum 



CC Etheostoma caprodes 



CENTRARCHID^. 

 Max. V. extending between tooth pads. 

 B. Papillae in perpendicular rows on either or both valves. 

 C. Rows ridge-like (or fold-like). 



D. Ridge-like rows on both valves . Ambloplytes rupestris 

 DD. Ridge-like rows on Mand. V. only 



Pigment spots on the papills . . Micropterus sabnoides 

 CC. Papilla? in rows on Mand. V. but not close enough to give 

 ridged appearance. Slight thickenings in V. under the 

 rows of papilla;. Clear margin . Eupomotus gibbosus 

 BB. Papillae not in perpendicular rows. 



E. PapiUie numerous on one or both. valves. 



F. Papillje very large, flat and crowded on both valves, giv- 

 ing tesselated appearance, and extending between 

 tooth pads Apomotus punctatus 



