THE CYPRINODONTS. 71 
Intestine less than twice the total length. Scales medium, flat, harsh. Both 
sexes rights and lefts. 
Fresh waters of Central America and the northern part of South 
America, venturing into brackish water near the shores. 
Three species of Anableps are all that are positively known ; these are 
easily distinguished by their colors or by their scales. Age, sex, or con- 
dition in the different types causes a considerable amount of modification in 
structure and appearance, for which allowances must be made. 
More than three narrow bands of brown along the flank ; Paor. 
50-55 scales on the lateralline. . . . . . . ~. anableps§ 77 
Less than three bands or uniform ; 
81-90 scales on the lateral line. . . . . + . ~ = microlepis 78 
A yellow band on mid-flank ; 
64-70 scales on the lateralline. . . . . . . . Dowii 79 
The fishes of this genus swim at the surface; their bodies are con- 
structed to withstand a great amount of buffeting. Integuments and 
bones are firm and strong. The opercular bones are moderately broad 
and are closely joined; with the urohyal and the wide vertical expansion 
of the shoulder girdle they furnish a rigid and close chamber for the gills. 
The body walls also are firm. The ribs are short; the broadness of the back 
is'due to the elongation of the parapophyses, which are wide and concave or 
troughed and chambered on the upper side. A greater number of vertebra 
in these species, than in those of other genera of the family, is in keeping 
with a greater comparative amount of activity. The evidence of the active 
Anableps, from the warmest of the waters, taken in connection with that of 
the more sluggish Orestias, from the cold lakes and streams of the Andes, 
does not support the conclusion recently advanced that warmer waters and 
greater activity are productive of a smaller number of vertebre, but proves, 
instead, that comparatively the greater number of vertebre obtains with the 
greater activity whether in warm waters or in cold, A prevalent idea gives 
this genus but a single nostril; there are actually two, the posterior being 
narrow and vertical and situated near the eye. The jaws are not firmly joined 
at the symphyses; the internarial process of the intermaxillaries is short, 
merely a blunt angle. The maxillaries do not form part of the edge of the 
mouth ; they do not meet; the upper half of each is wide, rounded, and 
extends horizontally toward the middle line in front of the skull. The skull 
is flattened, except at a strong frontal expansion that arches up and around 
