PLACOPHARYXX PAVEMENT-TOOTHED RED-HORSE 93 



flattened grinding surface; mouth larger and more oblique, and lips 

 thicker than in most species of Moxostoma. Fresh waters of south- 

 eastern United States; one species known. 



PLACOPHARYNX DUQUESNEI (Le Sueur) 



Le Sueur, 1817, J. Ac. Xat. Sci. 1'hila., I. 105 (Catostomus). 



J. & G., 14.3 (carinatus); M. V., 48 (carinatus); J. & E.. I, 198; N., 49 (carinatus); 

 J., 63 (carinatus); F., 80 (carinatus); F. F., II. 7, 441 (carinatus); L., 13. 



Body elongate, heavier forward, the form much as in Moxostoma 

 aureolum, but the back less elevated and the body somewhat less com- 

 pressed; depth 3.8 to 4.5 in length. Length IS to 30 inches. "Color dark 

 olive-green, the sides brassv, not silvery; lower fins and caudal orange-red " 

 (Jordan & Evermann). Head broad, flattish above, but less so than in 

 M . aureolum, cheeks vertical, chin flat; length of head 4.2 to 4.5. width 



6.2 to 6.7, depth 5.3 to 6 in body; interorbital space slightly convex, 2.1 to 



2.3 in head; snout blunt, squarish at tip, scarcely decurved, 2.3 to 2.4 in 

 head; mouth very large, the lower jaw oblique when the mouth is closed; 

 lips very thick and coarsely plicate, the folds broken in places into very tine 

 papillae in old specimens; lower lip very large, protruding when mouth is 

 closed, its halves meeting behind in an almost straight line; eye large, 4.3 

 to 5 in head. Dorsal fin with 12 or 13 rays, higher than long, its free 

 margin weakly concave, last ray half length of longest anterior ray; pec- 

 torals short, reaching but about | of distance from pectoral to ventral 

 basis; ventrals short, their tips 5 or 6 scales from vent. Scales 6, 43-47. 6 

 or 7 ; lateral line complete, almost straight. 



This fish has not ordinarily been separated readily from speci- 

 mens of Moxostoma without removal and examination of the char- 

 acteristic pharyngeal bones, but, as it seems to us, its very large 

 mouth and subtruncate lower lip, and its shorter lower fins should 

 enable one to distinguish it with ease from both Moxostoma ani- 

 surum and .1/. aureolum — the only species found in its range, so far 

 as is known, that resemble it at all closely. 



Its branchial apparatus is not notably different from that i >f 

 Moxostoma, the gill-rakers being short and few, and effective only on 

 the upper part of the arch, the lower arm being, like that of Moxos- 

 toma, covered by a rigid pad. The species is very remarkably dis- 

 tinguished, however, by its heavy pharyngeal jaws and its thick 

 and strong pharyngeal teeth with conspicuous grinding surface. 

 These number about 30 on each pharyngeal, the upper ones minute 

 and useless rudiments, and the lower 10 very large, occupying about 

 two thirds the length of the arch — the lower 6, in fact, about 

 half of it. It is probable that this apparatus is related to i 

 preference for mollusks as food, but the number of specimens avail- 

 able for our examination has been too small to test this supposition. 



