122 TELEOSTEI: ACANTHOPTERI. — XX. 



tion. ' Thus Etheostoma is to be explained by the hypothesis of 

 the progressive adaptation of the young of certain Percince to a 

 peculiar place of refuge and a peculiarly situated food supply. 

 These are the mountaineers among fishes. Forced from the popu- 

 lous and fertile valleys of the river beds and lake bottoms, they 

 have taken refuge from their enemies in the rocky highlands, where 

 the free waters play in ceaseless torrents, and there they have 

 wrested from stubborn nature a meagre living. Although diminished 

 in size by their constant struggle with the elements, they have de- 

 veloped an activity and hardihood, a vigor of life and a glow of 

 high color, almost unknown among the easier livers of the lower 

 lands. Kotwithstanding their trivial size, they do not seem to be 

 dwarfed so much as concentrated fishes.'' 



Their colors are often very brilliant, the males of some species 

 being among the most brilliant fishes known. The sexes are usually 

 unlike; the females being generally dull and speckled. They 

 usually prefer clear running water, where they lie on the bottom 

 concealed under stones, darting, when frightened or hungry, with 

 great velocity for a short distance, by a movement of the large pec- 

 torals, then stopping as suddenly. They rarely leave the bottom, 

 and are never seen suspended in the water. A few species prefer 

 a sandy bottom, where they lie buried in the sand, with only the 

 eyes visible. The Darters feed chiefly on the larva of Diptera. 

 The largest reach a length of 8 inches, but the average is about 21 

 inches. (The name Etheostoma is said by Rafinesque to mean 

 " various mouths " {erepos, various ; a-Tofia, mouth ?), the three species 

 known to him caprodes, blennioides, and fldbe.Uare, differing much 

 in this respect.) 



o. Body extremely elongate, hyaline, subterete, the belly mostly naked; 

 lateral line complete; head, long, pointed; gill membranes somewhat 

 united. 

 b. Premaxillariea protractile ; dorsal spines 7 to 11. 



c. Anal spine single; A. nearly as large as 2d D. (Ammociypta ' 

 Jordan = Pleurolepis Baird.) 

 d. Cheeks and opercles scaly. 



322. E. pellucidum Baird. Sand Darter. Scales of body 

 not very rough, only those along lateral line and on tail well imbri- 

 cated ; nape thinly scaled, becoming usually whoU}- naked on median 

 line; belly naked; maxillary barely reaching the large eye; P. 

 short. Translucent, finely dotted above ; a series of small square 

 olive blotches along back, and another along lateral line, the latter 

 connected by a gilt band ; fins pale. Head 4^ ; depth 7. D. X- 10. 

 A. I, 8. Scales 6-75 -X. Vert. 44. L. 2^. Ohio Valley and 

 N. W., abounding in clear sandy streams, where it buries itself in 

 the sand by a sudden plunge, and lies with only the eyes uncovered. 

 ' dfinot, sand ; KpvnTo^, concealed. 



