ETHEOSTOMA 303 



those along its sides are small and inconspicuous. In an aquarium 

 with sand on the bottom, it was seen to bury itself in a few seconds by 

 first stirring up the sand with rapid beats of its tail, as it stood liter- 

 ally upon its head, then lying still as the sand settled again, and 

 quietly putting out its nose and eyes, leaving only these and the 

 front of its head to be seen. Notwithstanding its peculiar habits 

 and its nice adaptation to a special environment, it is among our 

 group of most typical darters, its most frequent associate in our 

 collections being Hadropterus phoxocephalus, and next to this, Ha- 

 dropterus as pro. 



Its food seems remarkably uniform, consisting, like that of so 

 many other darters, of dipterous larv£e, mainly Chironomus, and 

 larvae of May-flies, the former largely preponderating in the speci- 

 mens we have studied. 



Genus ETHEOSTOMA Rafinesque 



Body robust or rather elongate, considerably compressed, or greatly 

 so; mouth varying in size, terminal or subinferior; premaxillaries not 

 protractile; teeth usually present on vomer and palatines; vertebrse 33 

 to 39, usually 36 (15+21); pyloric caeca 3 or 4; belly with ordinary 

 scales. Species numerous, about 30; size small; coloration various, often 

 brilliant. 



A large group, difficult to characterize, including a wide range of 

 forms, which, however, agree in having the premaxillaries non-pro- 

 tractile, and differ from all the preceding genera (except possibly 

 Diplesion) in having the cranium more elevated behind the eyes — 

 ri-shaped.* These fishes are, as a rule, more or less compressed, and 

 deeper bodied than such forms as Cottogaster, Boleosonia, and Ha- 

 dropterus. In this group are found our most brilliantly colored- 

 darters, bright red and blue in gaudy display on both body and 

 fins prevailing in the dress of many species. 



Key to the Species of ETHEOSTOMA found in Illinois 



a. Lateral line usually complete, occasionally 2 to 6 pores lacking. 



b. Gill-membranes joining broadly across the isthmus, distance from muzzle 



to their angle 40 to 50 per cent, greater than from muzzle to back of 

 orbit zonale. 



bb. Gill-membranes scarcely connected, distances to angle and to back of orbit 

 not far from equal camurum. 



*The forms (flabellarc, obeyensc, and squamiceps) with low dorsal fin and black 

 humeral spot (see key) seem to agree in having the parietals less arched than is 

 usual in Etheostoma, and shaped in cross-section more nearly as in Boleosoma. 



