MOXOSTOMA RED-HORSE 91 



This species, much the most abundant of the Illinois red-horse, 

 occurs outside our limits from the St. Lawrence and the Hudson 

 rivers through the Great Lakes to the Missouri River, north to 

 Winnipeg and the Assiniboin, and southward to Arkansas and 

 Georgia. In this state it is much the commonest in the northern and 

 eastern two thirds of our area, showing a tendency, like the pre- 

 ceding species, to avoid the turbid waters of southern Illinois, al- 

 though present in the clearer waters south of the lower Illinoisan 

 glaciation. It occurs in 148 of our collections, most abundantly, in 

 proportion to the number made, in the Rock River and the north- 

 west basins, and in the Kaskaskia and Wabash systems. It has 

 been taken by us, however, in all the other stream systems except 

 that of the Big Muddy. It is much the commonest in creeks and the 

 smaller rivers, the numbers found in the larger rivers being only half 

 the normal ratio for the species, and those in lakes and sloughs a 

 fourth that ratio. Its preference for swiftly flowing streams and its 

 avoidance of a mud bottom are also conspicuously shown by our 

 data of ecological distribution. 



This red-horse is not tenacious of life, but dies quickly in the 

 aquarium if the water is in the least impure. It also readily suc- 

 cumbs to impure conditions of its native waters such as are likely to 

 occur in midsummer, sometimes perishing in vast numbers and 

 stranding along the banks when violent summer rains, following 

 long periods of drought, overload the streams with mud and de- 

 composing vegetation. 



It spawns in April and May, ascending the smaller streams for the 

 purpose. Females taken from the Illinois River at Meredosia May 

 -5, 1899, were already spent. 



MOXOSTOMA BREVICEPS (Cope) 

 (short-headed red-horse) 



Cope 1870, P. Am. Phil. Soc, 478 (Ptychostomus) . 



J. & G., 141 (anisurum and (?) aureolum); M. V., 48 (crassilabre) ; J. & E., I, 196; 



N., 49 (Teretulus aureolum); J., 63 (Myxostoma aureolum); F., 80 (aureolum); 



F. F., II. 7, 444 (aureolum); L., 12 (macrolepidotum) . 



Body subfusiform, moderately compressed, rather deep under front 

 of dorsal, in form much like a Coregonus; depth 3.8 to 4.4 in length. 

 Size moderate, our largest specimens about 15 inches in length. Color 

 pale yellowish olive, with a faint coppery tint on sides in predorsal region ; 

 rest of sides and caudal peduncle very light pea-green, grading to whitish 

 or dull silvery lower down and on belly ; dorsal very pale olive, scarcely 

 dusky; caudal light reddish outward, olive near base; lower fins salmon 



