136 OSTARIOPHYSI. 
Hab. Guatemaua, Rio San Gerénimo ! (Salvin). 
Here described from the type, a specimen measuring 135 mm. in total length. 
16. Rhamdia polycaulus. (Tab. XXII. fig. 3.) 
Pimelodus polycaulus, Giinth. Cat. Fish. v. p. 181 (1864) ‘ 
Rhamdia polycaulus, Jord. & Everm. Bull. U.S. Nat. Mus. xlvil. 1896, p. 153°. 
Depth of body 52 in the length, length of head 53. Breadth of head 11 in its length, length of snout 24, 
diameter of eye 5, interorbital width 31. Lower jaw shorter than the upper ; width of mouth 2 the 
width of head. Maxillary barbel extending to posterior end of pectoral. Head covered with smooth 
skin; occipital process short, triangular, extending + of the distance from its base to the origin of dorsal. 
6 gill-rakers on the lower part of anterior arch. Dorsal I 6; spine slender, fin rounded, last ray cleft to 
the base. Length of adipose fin 24 in the length of the fish. Anal 15. Humeral process extending 
nearly to end of pectoral spine, which is less than 3 the length of the fin and + the length of head. 
Ventrals inserted behind the last dorsal ray, extending 2 of the distance from their base to the origin of 
anal. Caudal moderately notched. Least depth of caudal peduncle 14 in the length of head or in the 
distance from anal to base of caudal. Brownish. 
Hab. Guatema.a, Rio San Gerénimo ! (Salvin). 
Here described from the type, a specimen measuring 115 mm. in total length. 
17. Rhamdia rogersi. (Tab. XXIII. fig. 1.) 
Pimelodus rogersi, Regan, Ann, Mag. N. H. (7) xix. 1907, p. 259°. 
Depth of body 6 in the length, length of head 5. Breadth of head 11 in its length, length of snout 3, 
diameter of eye 6, interorbital width 8. Lower jaw shorter than the upper; width of mouth 2 the 
width of head. Maxillary barbel extending to middle of pectoral fin. Head covered with smooth skin ; 
occipital process short, slender, extending about } of the distance from its base to the origin of dorsal. 
7 gill-rakers on the lower part of anterior arch. Dorsal I 6; spine slender, fin rounded. Length of 
adipose fin about 4 in the length of the fish. Anal 12-14, when laid back nearly reaching the vertical 
from the end of adipose fin. Humeral process extending about to the middle of pectoral spine, which 
has the inner edge serrated and measures nearly 3 the length of the fin or nearly 2 the length of head. 
Ventrals originating behind the last ray of dorsal, extending 4 the distance from their base to the origin 
of anal. Caudal slightly notched. Least depth of caudal peduncle about 13 in the length of head or 
14 to 2 in the distance from anal to base of caudal, Brownish. 
Hab. Costa Rica, Irazu ! (Rogers). 
Here described from the types, four specimens measuring up to 130 mm. in total 
length. 
18. Rhamdia laticauda. 
Pimelodus laticaudus (Heck. MS.), Kner, Sitzungsb. Ak. Wien, xxvi. 1857, p. 420° ; Giinth. Cat. 
Fish. v. p. 127 (1864) *. 
Rhamdia laticauda, Jord. & Everm. Bull. U.S. Nat. Mus. xlvii. 1896, p. 152°. 
Evidently allied to the preceding, differing at least in the longer barbels and the longer adipose fin. 
Hab. Muxico}. 
Total length about 220 mm. 
