148 TELEOSTEI: ACANTHOPTERI. XX. 



Arctic fishes, numerous, 35 to 50. Genera 40; species 150, mostly 

 of the springs, rock-pools, and seashores of Arctic regions ; a few in 

 the deep sea. Singular fishes, mostly of small size, and of little 

 value as food. The fresh-water species are very destructive to 

 eggs of other fishes. 



a. Spinous D. longer than soft part, of more than 14 spines. (Hemitrip- 



terince.) 



b. Spinous D. deeply notched, the anterior spines highest; skin with prickles 

 and warts; teeth on vomer and palatines; gill membranes free from 



isthmus ; no slit behind last gill HEMITRIPTERUS, 186. 



aa. Spinous D. shorter than soft part, of less than 13 spines; dorsal spines not 



concealed; gill openings not very small. V. present. ( Cottinee.) 

 c. Vomer with teeth. 



d. Slit behind last gill obsolete or reduced to a round pore; skin with- 

 out true scales. 



Gill membranes broadly united to the isthmus, not forming a fold 

 across it; head feebly armed; palatine teeth few or none. 



COTTUS, 187 

 ee. Gill membranes free from isthmus or else forming a broad fold 



across it; head well armed. 

 f. Palatine teeth none ; skin naked or prickly. 



ACANTHOCOTTUS, 188. 



ff. Palatine teeth well developed ; skin smooth. 



ARTEDIELLUS, 189. 

 dd. Slit behind last gill small, but evident; no palatine teeth. 



g. Skin smooth; gill membranes not quite free from isthmus; 

 preorbital, etc., strongly cavernous. . TRIGLOPSIS, 190. 

 gg. Skin with minute prickly scales, and with plates along back 

 and lateral line ; gill membranes free from isthmus. 



TRIGLOPS, 191. 



OC. Vomer without teeth; preopercular spine antler-like; a fold across 

 isthmus and no slit behind last gill; no scales. 



GYMNACANTHUS, 192. 



186. HEMITRTPTERUS Cuvier. (wu-, half ; Tpeis, three ; 

 irrfpov, fin.) 



404. H. americanns (Gmelin). SEA RAVEN. Head large, 

 with many humps and ridges above. Brown, body and fins much 

 variegated with blackish. Head 2f ; depth 3f . D. IV, XII, 1, 12. 

 A. 13. Lat. 1. 40. L. 18. Cape Cod to Arctic Sea. 



187. COTTUS (Artedi) Linnaeus. ( Uranidea DeKay.) MILLER'S 

 THUMB. (Ancient name of C. gobio, from KOTTOS, head.) 



a. Palatines with teeth; ventrals I, 4 (the spine obscure). 

 b. Preopercular spine large, as long as eye, strongly hooked upward ; skin 

 above with coarse prickles (Tauridea Jordan & Rice). 



405. C. ricei Nelson. Head broad, body contracted at base of 

 tail. Olivaceous, finely speckled. Head 3f ; depth 5. D. VIII -1 7. 

 A. 12. L. 2J. Lake Mich, and L. Ontario, rare. (To Frank L. 

 Rice.) 



