CARPIODES CAIU'-SUCKERS 



79 



FIG. 19 



This species, unlike the others of its genus, is most abundant 

 in northern Illinois and least so in the southern part of the state. 

 It is almost wholly wanting from our southern Illinois collec- 

 tions made within the area of the lower Illinoisan glaciation. 

 Like the preceding species, however, it is found chiefly in the 

 smaller rivers and creeks, nearly twice as frequently in the latter 

 as in the rivers of larger size. It ascends small streams freely 

 at the time of the spring floods. In 1898 it spawned at Havana 

 about April 15. The snout of the male is tuberculate in the 

 spawning season. / 



, 



CARPIODES THOMPSONI AGASSIZ 



LAKE CARP 



(MAP XV) 



Agassiz, 1855, Amer. J. Sci. Arts, XIX, 76. 



J. & G., 119; M. V., 45 (Ictiobus); J. & E., I, 167; N., 49 (Ichthyobus) ; J., 65 (thomp- 

 soni and (?) selene) ; F., 81 (Ictiobus cyprinus, part). 



Body elongate, subfusiform, the back little arched and the ventral line 

 nearly straight, in general form and proportions very close to C. carpio, 

 depth 2.8 to 3.2 in length. Larger than difformis and velifer, known to 

 reach a weight of 3 to 5 Ib, and said by lake fishermen to grow much larger. 

 Color not different from that of carpio. Head moderate, its length 3.7 to 

 4, depth 4.5 to 5.1, width 5.7 to 6.4 in length of body; snout long, bluntly 

 pointed, 3 to 3.4 in head; nostrils situated well back from end of snout, 

 distance from anterior opening to tip of muzzle greater than diameter of 

 eye; mouth narrower and longer than in the two preceding species, sub- 



