THE CYPRINODONTS. 123 
in length in the sexes. Pectorals short, not reaching the bases of the ven- 
trals. Scales medium, the smaller ones on the caudal rays were not included 
in the numbers given above. 
Olivaceous, yellowish to dark brownish, light to dark ; back darker, with 
or without a darker vertebral streak and darker centres to the scales ; belly 
light to whitish; opercle silvery. In some localities the color is very light, 
more or less blotched or clouded with large areas of darker. In the breed- 
ing season the fins are rather highly colored. 
The variety dineafus tends toward an increase in the number of fin rays 
and in the rows of scales; the color is darker on the centres of the scales, 
and the fins are darker toward their tips. 
The top of the head is commonly marked with whitish in the midst of 
darker; in many the crown is dark, unmarked. Little darker along the 
lateral line. 
Described from two-inch specimens. 
Dakota southward in tributaries of the Mississippi. 
Zygonectes Jenkinsii. 
Zygonectes jenkinsii Everm., 1892, B. U.S. F. Com., for 1891, 86, pl. 36, fig. 2, 1894, B. U.S. F. 
Com. for 1892, pp. 83, 87, 89, 92, 107, pl. 24, fig. 3. 
B. 5; D. 8-9; A. 11-12; V. 6; P. 14-15; Ll. 30-32; Ltr. 9-8; 
Vert. 15+ 18. 
Moderately elongate and slender, compressed posteriorly, depressed on 
the head, depth of a specimen of one and five eighths inches two ninths of 
the length to the base of the caudal. Head two sevenths of the length, 
excluding the caudal, narrowed forward, crown flat. Snout nearly as long 
as the eye, pointed, chin not very steep. Mouth wide, not much directed 
upward ; lower jaws longer, firmly joined ; upper short, protractile. Outer 
series of teeth conical, hooked, stronger near the symphyses; inner small, 
similar in shape to the outer. Eye large, little longer than snout, nearly one 
third of head, three fourths of forehead. All fins with rounded margins. 
Dorsal smaller than anal, originating above its fourth or fifth ray, or about 
midway from the base of the pectoral to that of the caudal. Pectorals 
reaching a vertical from the bases of the ventrals. Ventrals small. Caudal 
not as long as the head, median rays a trifle the longer. 
Light rusty olivaceous, edges of scales darker, belly golden to silvery, 
