LUCANIA.—RIVULUS. 81 
25 or 26 scales in a longitudinal series. Dorsal 11-13; origin equidistant from tip of snout and base of 
caudal, Anal 9-11; origin below middle of dorsal. Pectoral 2 the length of head. Caudal rounded. 
Olivaceous; edges of scales darker; a silvery lateral stripe; fins plain (@) or a dark spot at anterior 
edge of dorsal (¢ ). 
Hab. Coasts and rivers from Florida to Tamaulipas : 
Pensacola in Florida*; Indianola in Texas! ; Matamoros in Tamaulipas °. 
Here described from specimens from Florida, measuring up to 60 mm. in total 
length. 
8. RIVULUS, Poey, 1860. 
Rivulus, Giinth. Cat. Fish. vi. p. 327 (1866) ; Jord. & Everm. Bull. U.S. Nat. Mus. xlvii. 1896, 
p-. 662. 
Cynodonichthys, Meek, Publ. Columbian Mus., Zool. v. 1904, p. 101. 
Oviparous. Mouth rather small, with short lateral cleft ; rami of the lewer jaw firmly united ; teeth pointed, 
in bands, with an outer series of enlarged, curved, conical teeth. Margins of eyes not free. 
This genus comprises four species from Mexico and Central America, two from 
Cuba, and about eight from South America*. The head is rather broad and the 
body is somewhat elongate, subcylindrical anteriorly and compressed posteriorly. The 
snout is short, and the lower jaw projects a little beyond the upper; the lateral gape 
of the mouth is short, horizontal, and about on a level with the middle of the eye; a 
vertical cleft in front of the eye marks the posterior edge of the broad lower lip. The 
teeth of the outer series are rather few and strong, and do not extend on to the sides 
of the jaws; one or two of the lateral teeth of this series may be longer than the others. 
The rather short dorsal fin is placed further back than the longer anal. The pectorals 
are obtuse and are placed very low; the ventrals are small; the caudal is rounded or 
subtruncate. 
Synopsis of the Mexican and Central-American Species. 
I. Origin of dorsal over posterior part of anal, which ends below the middle of the dorsal. 
Dorsal 9. Anal 12. 42 scales ina longitudinal series . . . . . . . IL. flabellicauda. 
Dorsal 8. Analll. 38 scales in a longitudinal series . . . . . . . 2. tenuis. 
Dorsal 8. Anal 1l. 385 scales in a longitudinal series . . 2. + . 8. godmani. 
II. Origin of dorsal over middle of anal, which ends a little in advance of the 
end of the dorsal. Dorsal 9, Anal 11. 32 scales in a longitudinal series. 4. isthmensis. 
1. Rivulus flabellicauda. (Tab. X. fig. 6.) 
Rivulus flabellicauda, Regan, Ann. Mag. Nat. Hist. (7) xix. 1907, p. 64°. 
Depth of body 4% in the length, length of head 34. Snout shorter than eye, the diameter of which is 4 in 
the length of head; interorbital width 24 in the length of headt. _ 42 scales in a longitudinal series. 
* Haplochilus harti, Bouleng., from Trinidad, and H. peruanus, Regan, from Peru, belong to this genus, 
+ In this species and in R. opercularis the interorbital width is less than the interocular width. 
BIOL. CENTR.-AMER., Pisces, May 1907. M 
