RHAMDIA, 129 
B, Width of mouth 3 to 2 the width of head. 
1. Occipital process extending } of the distance from its base to the origin of dorsal. 
a. Breadth of head 14 in its length, interorbital width4. . . . . 3. nicaraguensis. 
6. Breadth of head 1 to 13 in its length, interorbital width 23 to 3. 
. Pectoral spine $ the length of head; least depth of caudal 
peduncle 3 in the length ofhead . . . ~ 4. doucardi. 
&. Pectoral spine 2 to } the length of head; least depth of caudal 
peduncle 13 to 24 in the length of head. 
* Length of snout 22 to 22 in the length of head, which is 44 to 
4? in the length of the fish (in specimens measuring up to 
280mm.) . ...... es. ~ + » 5. wagneri. 
** Length of snout 22 to 8 in the length of head (in: specimens 
measuring up to 280 mm.). 
Breadth of head 1} in its length, which is 43 in the length of the fish; least 
depth of caudal peduncle 12 in the length of head . . . . . 6. petenensis. 
Breadth of head 14 to 1? in its length, which is 34 to 42 in the length of the 
fish ; least depth of caudal peduncle 2 to 23 in the length of head’ . . . 7. guatemalensis. 
2. Occipital process extending ? of the distance from its base to the origin of dorsal; inter- 
orbital width 22 to 3} in the length of head. 
Maxillary barbel extending to origin of adipose fin; pectoral spines 2 to 4 the 
length ofhead . .. . . « 8. godmani. 
“Maxillary barbel extending to middle of dorsal fin “pectoral spine 4 1 the length 
ofhead. 2. 1 ew we ee we we we ee ee ee 9 microptera. 
3. Occipital process extending } of the distance from its base to the 
origin of dorsal; interorbital width 4 in the length of head . . . 10. managuensis. 
II. Caudal fin with a moderately deep notch, but the middle rays more than 4 as long as the longest. 
A. Occipital process extending 2 of the distance from its base to the origin of dorsal; pectoral 
. spine ? to $ the length of head. 
Pectoral spine with a finely serrated inner edge and a series of antrorse denticu- 
lations on the outer edge; maxillary barbel reaching origin of adipose fin 
(in a specimen of 105 mm.); analof l0rays , . . . . « - « + . LI. heteracantha. 
Pectoral spine with serrated inner and entire outer edge; maxillary barbel 
reaching middle of base of dorsal fin (in a specimen of 115 mm.) ; anal of 
Wyrays. 2. 6 6 6 6 we ee ew ww ew ew ww we 1D. Aypselura. 
B. Occipital process slender, extending + of the distance from its base to 
the origin of dorsal; pectoral spine nearly 2? the length of head; 
maxillary barbel extending to basal part of pectoral (in specimens 
measuring upto190 mm.) . . . . . ee 6 ee ew ee eo 18, brachycephala. 
C. Occipital process short, triangular, extending } or 4 of the distance 
from its base to the origin of dorsal; pectoral spine from less than 
1 to nearly ? the length of head. 
1. Humeral process not reaching middle of pectoral spine; length of 
adipose fin 82 to 44 in the length of the fish; anal of 11 or 12 rays. 14. underwoodi. 
BIOL. CENTR.-AMER., Pisces, November 1907. S 
