ETHEOSTOMTD^. LXXXIX. 215 



Physostomi of later writers; but however different the 

 extremes of each (as Percoids and Cyprinoids) may be, 

 the intervening forms are too closely related to render 

 it possible to characterize them as distinct orders. 



SUB-OEDER-ACAISTTHOPTEEI. 



( The Spiny-rayed 'Fishes.) 



FAMILY LXXXIX. ETHEOSTOMID^E. 



(The Darters.) 



Fresh water fishes of small size, closely related to the 

 Percidce, but so peculiar in many respects that it seems 

 preferable to consider them as forming a distinct family. 

 Dorsal fins two, generally connected by membrane at the 

 base, the second and often both dorsals high and large ; 

 anal usually well developed, with one or two spines; 

 pectorals (except in one or two species) very large and 

 broad, often reaching beyond base of anal; caudal large, 

 rounded or slightly forked; scales ctenoid, sometimes 

 absent on neck or belly, or both; head usually more or 

 less scaly; teeth well developed on jaws and usually 

 on vomer; eyes large; air bladder rudimentary; "sub- 

 orbital arch incomplete." Colors often very bright; 

 species of Pcecilichthys and Diplesium being the most 

 brilliantly colored fresh water fishes known ; sexual differ- 

 ences usually recognizable, the females being as a rule 

 duller in color and more speckled or barred. In most 

 species there is a dark streak from eye to snout, and 

 often a dark vertical bar below the eye. Genera ten, or 

 fewer; species about thirty, all belonging to the U. S. 

 and Mexico, east of the Rocky Mountains, being most 

 abundant in the Mississippi Valley, where sometimes all 

 the genera may be found in the same stream. 



