ETHEOSTOMA 303 



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 literally 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, Hadropterus aspro. 

 Its food seems remarkably uniform, consisting, like that of 

 so many other darters, of dipterous larvae, mainly Chironomus, 

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

 specimens we have studied. 



Body robust or rather elongate, considerably compressed, or greatly 

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

 tractile; teeth usually present on vomer and palatines; vertebrae 33 to 39, 

 usually 36 (15+21) ; pyloric cseca 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 premaxil- 

 laries non-protractile, and differ from all the preceding genera 

 (except possibly Diplesion) in having the cranium more elevated 

 behind the eyes Q-shaped.* These fishes are, as a rule, more 

 or less compressed, and deeper bodied than such forms as 

 Cottogaster, Boleosoma, and Hadropterus. 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. 



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. 



aa. Lateral Hne always more or less incomplete, the number of pores lacking 



usually 10 to 30, rarely as low as 5. 



* The forms (flabellare, obeyense, 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 Etheosloma, 

 and shaped in cross-section more nearly as in Boleosoma. 



