148 TELEOSTEI: ACANTIIOPTERI. — XX. 



Arctic fishes, nunu'roiis, 35 to 60. (u'lUTii 40; species 150. mostV 

 of the sprinj^s, rock-pools, and seasliores of Arctic rejrions; a few in 

 the deep sea. ISiiij^idar fishes, mostly of small size, and of little 

 vulne as food. 'Ihe fresli-water sj)ecies are very destructive to 

 eggs of other fishes. 



a. Spinous D. longer than soft part, of more than 14 spines. {Uemitrip- 

 terina;.) 

 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 Hkmitiui'tkhi's, 186. 



aa. Spinous I), shorter thau soft part, of less than 13 spines; dorsal spines not 

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

 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; jialatine teeth few or none. 



COTTUS, 187. 

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

 across it; head well armed. 

 f. Palatine teeth none; skin naked or prickly. 



ACAKTHOCOTTUS, 188. 



ff. Palatine teeth well developed; skin smooth. 



Artkdiellus, 189. 

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



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

 prenrbital, etc., strongly cavernous. . Tkiolopsis, 190. 

 g(j. Skin with minute prickly scales, and with plates along back 

 aud lateral line; gill membranes free from isthmus. 



T1UGI.0P8, 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. (Jitxi-, half; rpcir, three; 

 nrfpov, fin.) 



404. H. americanus ((Jmelin). Sea Ravkn. Head large, 

 with many humps and ridges above. Brown, bo<ly 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 

 Tm:Mn. (Ancient name of C. gohio, from kottos, head.) 



o. 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 (Tnuridea .Jordan & Rice). 



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

 tail. Olivaceous, finely speckled. Head 3| ; depth .")J. D. VIII -17. 

 A. 12. L. 2^. LakcMich. and L. Ontario, rare. (To Frank L. 

 Rice.) 



