CARPIODES CARP-SUCKERS 



79 



Fig. 19 



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

 northern IlHnois and least so in the southern part of the state. It 

 is almost wholly wanting from our southern Illinois collections 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) 



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 lb, 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 le;ngth 

 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, subterminal and somewhat oblique, the tip 



