CYPRINIDA.—ICTIOBUS. 143 
§ Intestine elongate, with several convolutions ; pharyngeal teeth compressed, 
scarcely hooked, with broad grinding-surface, in a single series, 4—4. 
Scales large, less than 60 in a longitudinal series . . . . 7. Hysoenaruus. 
Scales small, 60 or more in a longitudinal series . . . . . . . . . 8, ALGANSEA. 
§§ Intestine comparatively short; pharyngeal teeth sub- 
conical, scarcely hooked, wide apart, in 2 series, 
5,2—2,4 . 2. 2. 2. ww ewe ew «69. Prycnocnertus. 
§§§ Intestine comparatively short; pharyngeal teeth compressed and hooked, 
without or with narrow grinding-surface, not set wide apart. 
{ Pharyngeal teeth in 2 series, 4-6, 1-2—2-1, 4-6 . 10. Levciscvs. 
Pharyngeal teeth usually in a single series, 4—4; sometimes a second 
yng y § ’ 
series of 1 or 2 small teeth. 
Lips normal; scales rather large, 45 to 50 in a longitudinal series; ventral 
fins 10-rayed ee se ew 2 oe . ~ . . . . LL. Farcura. 
Lips normal ; scales rather large, 30 to 60 i In a longitudinal Series ; ventral 
fins 8-rayed. 2. 2. 1. 1 ew ey we . ~ . « + « « . 12, Norrorts. 
Lips normal ; scales small, 85 to 95 in a longitudinal series . . . . . 13. Evarra. 
Lower lip forming a fleshy lobe on each side . . . . . . ~~. . 14. Paenacosius. 
t+ Gull-rakers very long, slender, and numerous . . . 15. XysrRosus. 
** Pharyngeal teeth cylindrical, with obtusely convex apices, 
in a single series, 3 in number on each side . . . . 16. Srypopon. 
6. First dorsal ray more or less enlarged and spinous or surrounded by thick skin, 
separated by a membrane from the second ray. 
Jaws without hard sheaths . . . 2 ee ww ee) hl dL, PimepHaces. 
Jaws with hard sheaths, forming cutting plates 2 ee ew eh) 6. «18. Cocntoenaruts. 
B. A small barbel at or near the end of each maxillary. 
1. Mouth terminal, oblique. 
Scales rather large, 45 to 50 ina longitudinal series. . . . . . . . 19, Yuriria. 
Scales smaller, 55 to 75 in a longitudinal series . . . . . . . . . 20. Covssivus. 
2. Mouth subterminal or inferior. . 
a. Premaxillaries protractile. 
Scales large, less than 60 in a longitudinal series . . . . . . . . . 21. Hysopsis, 
Scales smaller, 60 to 90 ina longitudinal series . . . . . . . . . 22, Acosta. 
5. Premaxillaries not protractile . . . . . . . . . . . 23, RHINICHTHYs. 
1. ICTIOBUS, Rafin., 1820. 
Ictiobus and Carpiodes (Rafin.), Jord. & Everm. Bull. U.S. Nat. Mus. xlvii. 1896, pp. 163, 165. 
This genus is at once distinguished from other Mexican Catostomine by the 
elongate dorsal fin. It comprises about ten species, ranging from the region of 
the Great Lakes to Guatemala. 
