308 MR. C. TATE REGAN ON THE 
Key to the Species. 
I. Adipose fin composed of a well-developed, freely movable spine, posteriorly attached by a 
membrane to the caudal peduncle. 
A. Ventrals originating well in advance of the dorsal, extending }-} of the distance from 
their base to the anal opening. 
'Yeeth of the outer series of the pramaxillaries all bicuspid; inter- 
ocular width 32 times in the length of head. . . . . . « 1. A. homodon Rgn, 
Lateral teeth of the outer series of the premaxillaries unicuspid ; 
interocular width 5 times in the length ofhead. . . . . . 2. A. boulengeri Rgn. 
B. Ventrals originating nearly below the first dorsal ray, extending to the anal opening. 
Teeth of the outer series of the prmaxillaries mostly bicuspid ; 
length of head 3}-3% times in the totallength. . . . . . 3. A. guentheri Bigr. 
‘Teeth of the outer series of the pramaxillaries mostly unicuspid ; 
length of head 4 times in the total length . . . . . . . 4. A. cyclopum Humbdt. 
II. Adipose fin, if present, elongate, with or without a small spine. 
A. Outer series of teeth of the premaxillaries mostly unicuspid, more or less acute ; 
mandibulary teeth bicuspid ; nasal flap not produced as a barbel. 
1. Ventrals originating below, or nearly below, the first dorsal ray. 
a. Adipose fin weakly or moderately developed ; pectoral spine not extending to middle 
of ventral. 
a. Adipose fin with a small spine which is completely imbedded in the adult ; barbel 
extending to the gill-opening, or at least } of the distauce from its base to the 
gill-opening. 
Ventrals extending 2 of the distance from their base to the anal 
opening ©: = «= eee - . | een. ty AOU TIDE Dae 
Veutrals extending 3-7 of the distance from their base to the anal 
opening ; distance from base of last anal ray to caudal 43-5 times 
im the'tétal length . 9.0% a =P we. 2. 2b 26, Aieigennapmee 
Ventrals extending 3-4 of the distance from their base to the anal 
opening ; distance from base of last anal ray to caudal 6 times 
in the'total length, . «+. 5 «ab tt.,<9 4 eee +, ce hg ad eee eae 
8. Adipose fin without spine. 
Barbel extending 4-2? of the distance from its base to the gill- 
QUEMINE . on +, vo | a cs pep REE =<) < fo. ae aa Blgr. 
Sarbel extending to, or nearly to, the gill-opening . . . . . . 9. A. brachycephalus Gthr, 
b. Adipose fin strongly developed ; pectoral spine extending beyond middle of ventral. 
a. Ventrals extending to the anal opening; barbels nearly to the gill-opening or 
beyond. 
a 
