88 FISHES OF ILLINOIS 



feeder which has become especially adapted to the search for 

 insect larvae occurring in rapid water under stones. It feeds, so 

 far as our observations go, almost wholly upon aquatic larvae, 

 mainly those of day-flies, more than half of the food of the speci- 

 mens examined consisting of a single form (Coenis) abundant 

 under stones. 



A few aquatic larvae of a gnat (Chironomus) , and some 

 other insect remains, with an insignificant ratio of small bivalve 

 mollusks, were the other elements of its food. 



It ascends the swifter brooks in spring, no doubt for spawn- 

 ing, although its habits of reproduction are not known. It is 

 sometimes used for food, but has virtually no economic value. 



Genus MOXOSTOMA Eafinesque 



RED-HORSE 



Body more or less elongate, usually more or less compressed; mouth 

 inferior; lips with transverse plica?, the folds rarely so broken up as to form 

 papillae; posterior fontanelle always well open; supraorbital bone wanting; 

 suborbitals very narrow; pharyngeal bones weak, the teeth rather coarser 

 than in Erimyzon and Catostomus; vertebrae (aureolum, breviceps) 39 to 41; 

 ribs 15 to 17; dorsal rays 11 to 17, usually about 13; scales large, usually 

 about 44 in the median lateral series; lateral line well developed; air-bladder 

 with 3 chambers. Males in spring with lower fins reddened (whence the 

 common name), and with anal rays swollen and tuberculate. 



United States, east of the Rocky Mountains; species 

 numerous; 3 species found in Illinois. 



The gill-rakers of the red-horse are largely modified into 

 transverse leaf -like plates with notched edges projecting in 

 triangular outline only a little beyond the margin of the thick, 

 strong arch. Those of the anterior gill are more elongate, but 

 stout and triangular, and about three fourths as long as the 

 gill-filaments, the whole branchial apparatus being thus coarse 

 and strong, better adapted to hold hard and somewhat bulky 

 objects than to strain from the water small and delicate ones. 

 The pharyngeal jaws are moderately heavy, with strong teeth, 

 and the intestine is small and about one and a fourth times the 

 length of the head and body. Quite in correspondence with 

 these features of the feeding apparatus, the main food of the 

 red-horse consists of water-snails of various species, and small 

 bivalve mollusks belonging to the genus Sphoerium. About a 

 third of the food of specimens examined by us consisted of insects, 

 practically all aquatic larvae. The vegetable matter present in 



