82 HAPLOMI. 
Dorsal 9; origin above posterior part of anal, which ends below the middle of the dorsal. Anal 12; 
origin equidistant from operculum and base of caudal. Pectoral 3 the length of head. Caudal sub- 
truncate. Brownish; edges of scales darker; vertical fins with some small darker spots; an ocellus on 
the upper half of the base of the caudal fin. 
Hab. Costa Rica, Juan Viiias (Underwood 1), San José (Biolley). 
Two specimens, the type, 70 mm. in total length, and a much smaller example not 
included in the description. 
2. Rivulus tenuis. 
Cynodonichthys tenuis, Meek, Publ. Columbian Mus., Zool. v. 1904, p. 101, fig. 27°. 
Allied to 2. godmani, but with smaller scales and a smaller eye (diameter 3% in the length of head in 
a specimen of 40 mm.). 
Hab. Mexico, El Hule in Oaxaca !. 
3. Rivulus godmani. (Tab. X. fig. 5.) 
Rivulus godmani, Regan, Ann. Mag. Nat. Hist. (7) xix. 1907, p. 65. 
Depth of body 44 to 5 in the length, length of head 32. Snout shorter than eye, the diameter of which is 3 
in the length of head and a little less than the interorbital width. 35 scales in a longitudinal series. 
Dorsal 8; origin above posterior part of anal, which ends below the middle of the dorsal. Anal 11; 
origin equidistant from operculum and base of caudal. Pectoral $ the length of head. Caudal sub- 
truncate or rounded. Olivaceous, with a more or less distinct darker spot on each scale; operculum 
blackish ; vertical fins dusky, the caudal with a narrow light edge, and below with a blackish intra- 
marginal stripe ; caudal ocellus sometimes present. 
Hab. GuateMaua (Godman). 
Two specimens, 40 mm. in total length. 
4, Rivulus isthmensis, 
Rivulus isthmensis, Garman, Mem. Mus. Comp. Zool. xix. 1895, p. 140°. 
Hab. Costa Rica, Rio San José t. 
4. CYPRINODON, Lacep., 1803. 
Cyprinodon, Jord. & Everm. Bull. U.S. Nat. Mus. xlvii. 1896, p. 670. 
Oviparous. Mouth small, with short lateral cleft; rami of the lower jaw firmly united; teeth incisor-like, 
tricuspid, in a single series. 
About eight species comprise this genus, which ranges from the United States to 
Brazil. In these the gill-openings are restricted from above, commencing only a little 
above the level of the pectoral fins. The Old-World genus or subgenus Ledias differs 
only in the greater freedom of the operculum. 
A few forms enter the sea and others are sometimes found in salt springs; they 
are very variable and difficult to distinguish; specimens without ventral fins are not 
uncommon. 
