92 FISHES OF ILLINOIS 



with paler, greenish margins. Head extremely short, subconieal, tapering 



both above and below to the tip of the pointed snout ; length of head 4.6 to 



5.4 in body, usually more than 5 in adults, width 6.6 to 7.6, depth 5.7 to 



6.7 ; interorbital space 1.9 to 2.4 in head, noticeably convex; chin convex; 



cheeks shallow, not vertically continuous to a flat 



chin as in aureolum and anisurum, a cross-section 



of the head in the orbital region not being squarish 



as in those species; snout 2.3 to 2.9 in head, not at 



all decurved ; mouth small, upper lip rather coarsely 



plicate, the folds shallow and not continued back 



to the inside of the lip; lower lip truncate behind, 



the two halves scarcely separated at the shallow 



incision, the coarse but shallow plicae evident in 



Pi G ' 23 front, but breaking up into irregular papillae pos- 



Lips of Moxostoma teriorly ; eye small in comparison with length of 



body, but contained 4 to 5 times in the very short 



head. Dorsal rays 12 or 13, the fin notably higher 



in front than behind, the last ray being less than half the length of 



the longest anterior ray, which is usually considerably longer than the 



base of the fin ; free margin of dorsal concave ; pectorals longer than the 



short head, but relatively shorter than in the two preceding species, 



scarcely reaching § of the distance from pectoral to ventral basis; 



upper lobe of caudal falcate, usually, though not always, longer than 



1' iwer. Scales 6, 43-45, 5 or 6 ; lateral line complete, nearlv straight. 



This species occurs in the Ohio Valley and the Great Lake region, 

 being especially abundant in Lake Erie. In the Mississippi Valley 

 it ranges up the Missouri to Cheyenne Falls. It is especially a 

 northern Illinois fish, only one of our collections made in the south- 

 ern part of the state containing it, and this falling outside the area 

 of tlie lower Illinoisan glaciation. It is about equally common in 

 central and northern Illinois, and has been more uniformly distrib- 

 uted, according to our observations, than the other species of its 

 genus, occurring in about equal frequency, relatively to the number 

 of collections made, in the larger rivers and in creeks and lakes, but 

 about twice as abundantly in the smaller rivers. It shows also con- 

 siderably less marked preference than the preceding species for 

 clear and swiftly flowing waters. 



Genus PLACOPHARYNX Cope 



(pavement-toothed red-horse) 



Suckers like Moxostoma in all respects, except that the ]>liarvne,ral 

 bones are much more developed and the teeth reduced in number, ihose 

 on the lower half of the bone very large, 6 to in in number, nearly cylin- 

 drical in form, but little compressed and with a broad and more or less 



