THE CYPRINODONTS. 151 
teeth with a shoulder, as in Anableps and Rivulus. Eye one and one- 
half times in the snout, twice in the interorbital space, and four and three 
fourths times in the head. Seales large ; on head and body to tips of pec- 
torals thick, convex, smooth, and glossy ; on hinder portion of body flat, 
thinner, with fine stria, not glossy; breast naked, more of the lower surface 
covered on this species than on O. Cuvieri or O. Pentlandii ; about four series 
of scales on the cheek; more or less of the top of the snout naked; verte- 
bral series irregular. Dorsal fin originating about half way from occiput to 
base of caudal, its third ray above the first anal ray, which is midway be- 
tween base of pectoral and caudal. Base of anal extending a couple of rays 
farther backward than that of dorsal. Caudal broad, as long as head, 
rounded on the posterior margin. Pectorals reaching little more than half 
the distance to anal. Intestine convolute, one and a half times to twice the 
total length. On old individuals the nape and back of the head become 
strongly arched, the latter becoming quite prominent, and the scales are lost 
from the interorbital space and forward. The thickness and the worn ap- 
pearance of the scales suggests a great deal of rubbing against the rocks 
or gravel. On specimens of three inches the convex and glossy scales are 
hardly to be detected; and those of two inches are much like the Funduli, 
the head and shoulders being less prominent and the body more compressed. 
As in the other species the main osseous support of the caudal is a single 
very broad fan-like ray, in which there is little or no evidence of fusion, 
passing directly backward from the vertebra. 
Eight inch specimens are olivaceous on the back, lighter to whitish on 
the lower half of the body. The scales being lighter colored in their cen- 
tres give the back a tessellated or reticulated appearance. The fins are 
brownish, more or less clouded. Young less than half grown are much 
lighter colored ; they have a narrow streak of darker along the middle of 
the flank, faint transverse bands or series of spots or blotches on back and 
fins, and a yellowish tint below the gills. In this stage snout and eye have 
about the same length. When about two inches in length the color is much 
lighter, there are transverse streaks of brown on the fins, clouded blotches, 
formed of puncticulations, on the flanks and in a somewhat irregular series 
along the middle, and the cheeks and a streak below the dark line on the 
middle of the side are silvery. The amount of silvery space on the lower 
half of the body varies greatly. 
Abundant in Lake Titicaca. 
