148 CONTEIBUTIONS TO NORTH AMERICAN ICHTHYOLOGY IV. 
dd. Upper jaw protractile ; teetli not molar. 
e. Teeth two-rowed, 2 teeth in the lesser row. 
/. Lateral line complete. 
g. Teeth siihconical, scarcely hooked, sharp-edged, wide apart, the long 
limb of the pharyngeal bone elongate. 
Ptychochilus, 100. 
gg. Teeth compressed, close-set, strongly hooked ; the pharyngeal hone of 
the nsual form. 
h. Caudal peduncle slender and elongate, the caudal fin widely forked, 
its basal rudiments much developed; scales very small ; 
head depressed Gila, lol. 
hli. Caudal peduncle stout ; basal rudiments of caudal little developed. 
Squalius, 102. 
ff. Lateral line incomplete PiioxiNUS, 103. 
ee. Teeth one-rowed. 
- Lateral line complete. 
g. Mouth of moderate size Leucos, 104. 
gg. Mouth extremely small Opsopceodus, 105. 
— Lateral line incomplete; teeth serrate Trych.eroi)OX, 106. 
JJ. Abdomen behind ventral fius compressed to an edge, 
the scales not passing over it ; anal basis usually elon- 
gate ; dorsal posterior. 
i. Abdomen in front of ventrals rounded ; anal basis rather long. 
j. Teeth 5-5, with griudiug surface and serrate edges. 
Notemigoxus, 107. 
jj. Teeth 2, 5-5, 2, entire, without grinding surface. Alburxus, 108. 
** Dorsal fin short, posterior, with a strong spine, composed of two, the posterior re- 
ceived into a longitudinal groove of the anterior ; inner 
border of the ventral fins adherent to the body ; teeth 
hooked, without grinding surface, in two rows. (Plago- 
2 >teriiia\) 
I. Body with small scales ; teeth 2, 4-4, 2 ; no barbels. 
Lepidomeda, 109. 
II. Body scaleless. 
m. Maxillary without barbel; teeth 1, 4-4, 1 Meda, 110. 
mm. Maxillary with a barbel ; teeth 2, 5-4, 2. 
Plagopterus, 111. 
#»# Dorsal fin elongate: dorsal and anal fins each preceded by a serrated spine; 
scales large; teeth molar; siiecies introduced. {Cij- 
jn'inino}.) 
ti. Barbels 4 ; teeth 1, 1, 3-3, 1, 1 Cyprixus. 
nn. Barbels none; teeth 4-4 Carassius. 
71 . — CAITIPOSTOMA Agassiz. 
Stone rollers. 
(Agassiz, Amer. Jonrn. Sci. Arts, 1855, 218: type Itutihis anomnhis Raf.) 
Body moderately elongate, little compressed. Mouth normal, the 
jaws with thick lijis and rudiment of a hard sheath. Premaxillaries 
protractile ; no barbel. Teeth 4-4, or 1, 4-4, 0, with oblique grinding 
surface and but a slight hook on one or two teeth. Air-biadder sus- 
