THE CYPRINODONTS. 143 
CYNOLEBIAS. 
Cynolebias Steind., 1876, Sb. Ak. Wien, LXXTIV, extr. p. 124. 
Head and body compressed, body deep, caudal pedicel medium. Chin 
steep, lower jaw massive, prominent, symphyses firm. Teeth subconical, in 
bands. Gill openings wide; membranes short, united for a short distance, 
free from the isthmus. Dorsal and anal with numerous rays, opposed, anal 
longer and originating a trifle farther forward. Ventrals small, bases near 
anal. Body cavity hardly half of the length to the caudal. 
Body and head are both more compressed in this genus than in Rivulus; 
the body is deeper in the forward half and rather more slender in the caudal 
section ; the fin rays are more numerous, and the base of the dorsal is longer. 
Compared with Pterolebias the body is deeper forward and has not the sharp 
edge between ventrals and caudal. The head also is more compressed, the 
snout longer, and the mouth more nearly horizontal. Four species have 
been described from La Plata river, and one from Pernambuco; of the five it 
does not appear that more than three are valid. 
Cheek, preopercular, scales in six or more series; Pace 
Ll. more than forty porosus 143 
Cheek scales in two or three series; 
Ll. less than thirty-five ; 
anal rays more than twenty-five Bellottii 144 
anal rays less than twenty-five maculatus 145 
Cynolebias porosus. 
Cynolebias poroms Steind., 1876, Sb. Ak. Wien, LXXIV, extr. p. 125, pl. 10, fig. 3; Perug., 1891, 
Ann. Mus. Civ. Gen., (2) X, 651; Eig, 1891, P. U. S. Mus., XIV, 65. 
Cynolebias elongatus St., 1881, Denk. Ak. Wien, XLIV, extr. p. 11; Eig., 189), P. U. S. Mus, 
XIV, 64. 
B.7; D. 17-18; A. 20; V. 5; P. 14; LI. ca. 45-48; Ltr. 21. 
Body compressed, depth at origin of dorsal nearly equal length of head, 
equal three tenths of the body without the caudal, or little more than one 
fourth of the total length. Back arched from head to hind end of dorsal. 
Pedicel of caudal medium. Head compressed, crown flattened, cheeks covered 
with scales, chin and throat naked. Eye small, lateral, hardly as long as 
snout, two ninths of head, one half of forehead. Anterior nostril a short 
tube. Mouth nearly horizontal; lower jaw longer, massive; chin steep; 
