52 TELEOSTEI: EVENTOUNATHI. XII. 



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



present, but minute] Ehinichthys, 59. 



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

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



dorsal behind ventrals Ehihichthts, 69. 



nn. Premaxillaries protractile. 



o. Teeth 4-4, or 1, 4-4, 1, orl, 4-4, 0; scales not rerj' small. 



Hybopsis, 60. 

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

 p. Head transversely convex above; teeth without grinding 



surface Couesius, 61. 



pp. Head flattened above; teeth with grinding surface; 



scales large Platygobio, 62. 



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 Semotilus, 63. 



gq. 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 Phoxinus, 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. 

 a. 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 NOTEMIGONUS, 66. 



49. CAMPOSTOMA Agassiz. (cafiTr^, curve ; crrofia, mouth.) 



87. C. anomalum (Rafinesque). Stone Luggek. Stone 

 Roller. Brownish, with a hrassy 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 •, <J 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 Camposloma alone 

 among all the vertebrates. D. 8;A.'7. Scales 7-63-8. Teeth 4-4. 

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

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

 variable. ' 



50. OXYGENEUM Forbes, (ogur, sharp ; ytvos, chin.) 



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

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

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



