52 TELEOSTEI: EVENTOGNATHI. - XII. 



xx. [Premaxillaries not protractile; scales very small; barbei 

 present, but minute] ..... KHINICHTHYS, 59. 



Ick. Maxillary with a small barbel at its extremity (rarely obsolete). 



n. Premaxillaries not protractile ; teeth 2, 4-4,2; scales small; 



dorsal behind ventrals ...... RHINICHTHYS, 59. 



nn. Premaxillaries protractile. 



o. Teeth 4-4, or 1, 4-4, 1, or 1, 4-4, 0; scales not very small. 



HYBOPSIS, 60. 

 oo. Teeth, 2, 4-4, 2 or 1. 



p. Head transversely convex above; teeth without grinding 

 surface ........... COUESIUS, 01. 



pp. Head flattened above; teeth with grinding surface; 

 scales large ........ PLATYGOBIO, G2. 



jj. Teeth in the main row 5-5 or 4-5. 



q. Maxillary with a minute barbel placed before its tip ; premax- 

 illaries protractile; teeth, 2, 4-5, 2, without grinding surface; 

 caudal fin symmetrical ....... SKMOTILUS, 63. 



qq. Maxillary without barbel; premaxillaries protractile; anal 



basis short. 



r. Teeth two-rowed, 2, 4-5, 2, or 2, 5-5, 2, strongly hooked; 

 scales moderate or small ...... PIIOXINUS, 64. 



[As above, the head broad and bluntish; the barbel so minute 



as to be indistinguishable, in the young of SEMOTILUS, 63.] 



rr. Teeth one-rowed, 5-5, with serrate edges; mouth very small, 



terminal; D. inserted over V. . . . OPSOPCEODUS, 65. 



ii. Abdomen behind V., compressed to an edge, the scales not crossing 

 it; anal basis elongate (the rays 12 to 18); teeth 5-5, with grind- 

 ing surface and serrate edges; gill rakers rather long; no bar- 

 bels; D. inserted behind V. ...... NOTEMIGCXNUS, 66. 



49. CAMPOSTOMA Agassiz. (Ka/zm;, curve ; o-rd/za, mouth.) 



87. C. anomalum (Rafinesque) . STONE LUGGER. STONE 

 ROLLER. Brownish? with a brassy lustre above, the scales mot- 

 tled ; a black vertical bar behind opercle ; iris orange ; D. and 

 A. each with a dusky cross-bar about half-way up, rest of the 

 fin in spring orange ; in spring with many rounded tuber- 

 cles on head and body ; young mottled brownish, the fins plain ; 

 scales crowded forward; intestinal canal six to nine times the total 

 length of the body, its numerous convolutions passing above and 

 around the air-bladder, an arrangement found in Campostoma alone 

 among all the vertebrates. D. 8; A. 7. Scales 7-53-8. Teeth 4-4. 

 L. 4 to 8. W. N. Y. to Texas, and Tenn. in small streams, every- 

 where abundant ; one of the most curious of American fishes. Very 

 variable. 



50. OXYGENBUM Forbes, (o&s, sharp ; yeVos, chin.) 



88. O. pulverulentum Forbes. Form of Moxostoma : head 

 small, conical ; mouth large, terminal ; gill rakers slender ; eye 4 

 in head ; 31 scales before dorsal ; breast scaly. Color pale, the 



