52 TELEOSTEI: EVENTOGNATHI. — XI. 
xx. [Premaxillaries not protractile; scales very small; barbel 
present, but minute] . . . . . Ruryicutuys, 59. 
kk. 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. 
Hysopsis, 60. 
oo. Teeth, 2, 44, 2 or 1. 
p. Head transversely convex above; teeth without grinding 
SliTfaee joc Hen ie - « »« « Covugsivs, 61. 
pp. Head flattened hae tenth. with grinding surface; 
scales large . « »\ js ss js |» » PLATYGORIO; 62; 
yj. Teeth in the main row 5-5 or 4-5. 
g- Maxillary with a minute barbel placed before its tip; premax- 
illaries protractile; teeth, 2, 4-5, 2, without grinding surface; 
caudal fin symmetrical . . . . . . . SEMOTILUS, 68. 
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 SEMorILus, 63.] 
rr. Teeth one-rowed, 5-5, with serrate edges; mouth very small, 
terminal; D. inserted over V. . . . Opsopaopus, 65. 
ai. 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. (kxayumn, curve; o7oua, mouth.) 
87. C. anomalum (Rafinesque). Stone LuGGer. STONE 
Rotter. 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 g 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. OXYGENEUM Forbes. (d£vs, sharp; yévos, chin.) 
88. O. pulverulentum Forbes. Form of Mozostoma: head 
small, conical; mouth large, terminal; gill rakers slender; eye 4 
in head; 31 scales before dorsal; breast scaly. Color pale, the 
