52 TELEOSTEI: EVENTOGNATHL — XII. 



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



present, but minute] Khinichthys, 59. 



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



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



dorsal behind vontrals 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, 61. 



]>p. 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. 



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 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. 

 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 Notemigonus, 66. 



49. CAMPOSTOMA Agassiz. (Kafinfj, curve ; arofxa, 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 Camposloma 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. OXYGENEUM Forbes. (6^vs, sharp ; yt'vos, 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 



