FISHES OF THE FAMILY LORICARIID&. 309 
Pectoral spine extending a little beyond middle of ventral ; adipose 
fin with a small nodule imbedded in the upper half of its 
posterior part ; anal opening at 2 of the distance from base of 
Mentrali to: orizinuotranall css) och a oc 5 cops) -« Yc he 4 «.. lO! 0d: chats Ren. 
Pectoral spine extending nearly to tip of ventral; adipose fin with 
a nodule imbedded in the upper half of its posterior part ; 
anal opening midway between base of ventral and origin of 
arto eee. co young fe ie. NE a8) Pe a LI Al parinoraies Ren. 
Pectoral spine extending to tip of ventral; adipose fin without 
LLNS Soe A ee ae oe eo eee | longifilis Stdr. 
8. Ventrals extending to the anal opening, barbel 
3-3 of the distance from its base to the gill- 
Opening, pectoral spine to middle of ventral . . 13. A. sabalo C. & VY. 
y- Ventrals extending 3 of the distance from their 
base to the anal opening, barbel to the gill- 
opening, pectoral spine to posterior } of ventral . 14. A. taczanowskii Blgr. 
2. Ventrals originating below the fifth dorsal ray . . . 15. A. prenadilla C. & V. 
B. Outer series of teeth of the premaxillaries all acutely 
bicuspid; nasal flap not produced as a barbel ; adipose 
fin moderately developed, without trace of aspine . . 16. A. Jissidens Regn. 
C. Outer series of teeth of the pramaxillaries all bicuspid, or 
the lateral teeth unicuspid. Nasal flap produced as a 
Dak be Mamet ci sie ic) ee gee ets = (fa lo A. feste Blegr. 
D. Outer teeth of both jaws compressed, expanded, some- 
times more or less distinctly bicuspid, usually distinctly 
incisor-like. 
Interocular width less than the distance from eye to posterior 
nostril; barbel not nearly reaching the gill-opening . . . . 18. A. peruanus Stir. 
Interocular width equal to the distance from eye to posterior 
nostril; barbel extending nearly to the gill-opening . . . . 19. A. simonsi Regn. 
1. ARGES HOMODON, sp. n. (Plate XXI. fig. 1.) 
Length of head 3% times in the total length. Interocular width a little less than 
the distance from eye to posterior nostril, 5} times in the length of head. Outer series 
of teeth of the preemaxillaries all bicuspid, more or less Y-shaped ; mandibulary teeth 
bicuspid; barbel extending beyond the gill-opening. First dorsal ray equal to 2 the 
length of head; pectoral spine extending to middle of ventral; ventrals originating 
well in advance of the dorsal, extending 2 of the distance from their base to the anal 
opening. Spine of the adipose fin well developed, freely movable, inserted at a distance 
