326 FISHES OF ILLINOIS 



The sculpins chiefly inhabit rocky pools and shores of northern 

 regions; many species found in inland waters; genera about 60; 

 species 250. None are valued as food. 



Key to Genera and Species of COTTIDjE found in Illinois 



a. Ventrals with a concealed spine and four soft rays Cottus. 



b. Preopercular spine short, usually inconspicuous, usually less than * eye; 



interorbital space nearly as wide as or wider than eye, 3.8 to 5.6 in head; 

 depth of caudal peduncle 1.5 to 2 in its length; maxillary to middle of 

 eye; dark cross-bars usually present ictalops. 



bb. Preopercular spine long, J to as long as* eye, strongly curved upward, back- 

 ward, and inward, the skin of the head carried upward by the spine on 

 each side in an ear-like manner; top of head flat, the interorbital space 

 very narrow, little more than half of eye and contained 8 times in head, 

 the' eyes directed nearly upward; caudal peduncle very slender, its depth 

 about 3.3 in its length; maxillary scarcely past front of orbit; color 

 spotted or mottled, without distinct cross-bars ricei. 



aa. Ventrals with a concealed spine and three soft rays Uranidea. 



c. Preopercular spine less than £ eye; interorbital space about half of eye, 7.5 



to 8.5 in head; caudal peduncle moderately slender, its depth 2.2 to 2.4 

 in its length; maxillary to middle of orbit; sides irregularly spotted, with- 

 out bars kumlienii. 



Genus COTTUS (Artedi) Lixx.eus 

 (miller's thumbs) 



Body fusiform, skin smooth or more or less velvety, prickles, if pres- 

 ent, not bony or scale-like; preopercle with a simple spine at its angle, 

 which is usually curved upward, its base more or less covered with skin, 

 rarely obsolete; gill-membranes separated by a wide isthmus, over which 

 the membranes do not form a fold; no slit behind fourth gill: villiform 

 teeth on jaws and vomer, and sometimes on palatines; dorsals nearly or 

 quite separate; ventrals each with a concealed spine and 4 soft rays; 

 lateral line present. These are sculpins of small size, inhabiting clear 

 waters of the northern portions of Europe, Asia, and America; species 

 numerous. 



COTTUS ICTALOPS (Rafinesque) 



(common sculpin; miller's thumb) 



Rafinesque, 1821), Ichth. Oh., 85 (Pegedictis). 



<", . II, 15S (richardsoni); |. X- G . <>"» (richardsoni) : M. V.. 149 (richardsoni) ; J. 

 & I.. II. 1950; X. il (Pegedichthys alvordi) ; J, 50 (Potamocottus alvord'i, 

 wilsoni. and meridionalis) ; F. F . 1 <>, 68 (Potamocottus meridionalis) ; F., 62 

 (Uranidea richardsoni); L , 30. 



Length 3 to 7 inches; body robust forward, subcylindrical, tapering 

 rapidly hack of spinous dorsal; depth 3.7 to 4.3; width about J depth; 



♦According to Jordan and Evermann; our single specimen with spine J of eye. 



