PLACOPHARYNX PAVEMENT-TOOTHED RED-HORSE 93 



grinding surface; mouth larger and more oblique, and lips thicker than in 

 most species of Moxostoma. Fresh waters of southeastern United States; 

 one species known. 



PLACOPHARYNX DUQUESNEI (L E SUEUR) 



Le Sueur, 1817, J. Ac. Nat. Sci. Phila., I, 105 (Catostomus). 



J. & G., 143 (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 aureo- 

 lum, but the back less elevated and the body somewhat less compressed; 

 depth 3.8 to 4.5 in length. Length 15 to 30 inches. "Color dark olive- 

 green, the sides brassy, 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 fine 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; pectorals 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 

 specimens of Moxostoma without removal and examination of 

 the characteristic 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 anisurum and M. 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 of 

 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 Moxostoma, covered by a rigid pad. The species is very 

 remarkably distinguished, 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 a preference for mollusks as food, but 



