ANNOTATED LIST OF THE SPECIES 369 
only slightly exceeding the length of the head, the dorsal profile straight, or nearly 
straight, on the head, while convex in agassizii; head pointed, its depth through 
center of eye less than that of caudal peduncle; mouth wider, equal to interorbital, 
lips thickened, fleshy; little enlargement or convexity of the shoulder scales; 
median fins more rectilinear, but caudal more rounded. Colors in alcohol, red- 
brown upper parts, merging into maroon below; fins unmarked or with dark band 
at base of dorsal and anal. 
A comparison of smaller specimens reveals such differences as the following: 
More elongate than O. agassizii, head more pointed; more rounded form: 
dorsal profile less convex; crown and snout narrower, interorbital space narrower; 
eye less oval; chin less vertical; fins larger in both dimensions, pectoral especially 
broad, median fins considerably broader, but caudal not so elongate in extreme 
young; colors begin early to differentiate as above. Thick lips are a good character 
for separating adults, but I do not find this consistent in the smaller specimens. 
Considering the small size and juvenile character of the Valenciennes types, 
less than 4 inches, our young specimens of this species could readily be confused 
with them, especially with their great variation and the metamorphoses through 
which they pass. 
I find the present species, by reason of its more minnow-like form and less 
specialized scales, to be nearer than O. agassizii to the primitive Orestias stock. 
Since nowhere in the northern range of the genus have we collected large specimens 
similar to the O. agassizii of Lake Titicaca, and since all the larger specimens taken 
in the north are identical with the present type, I am convinced of their complete 
isolation geographically. The great gorges of the Apurimae and other streams 
appear to be an effective barrier between them. 
Description of the type, 120 mm. long, Lake Chinchaycocha, (15238). 
Dorsal contour straight on the head, faintly arched above the opercle, slightly 
convex to origin of the dorsal fin, descending slightly along its base to rectilinear 
caudal peduncle. Contours rounded, never angular. Caudal peduncle slightly 
longer than dorsal basis. 
Width in depth 1.5, shghtly greater than length of head, and 3.5 in body 
length; eye 4.8 in the head, equals snout, 1.4 in the interorbital space; head 3.7 
in the body length; snout narrow, equals width of mouth and length of opercle; 
chin roundly pomted, mouth oblique, crescentic in front view, lips thickened and 
fleshy; teeth sparse. 
Scales showing striae, becoming moderately thickened on forward parts, but 
well-embedded, not deciduous anywhere; scale-rows somewhat irregular on nape, 
head, and shoulder; nowhere polished or granular; few scattered scales on suborbital 
area; smooth, tightly embedded, but not dense, on cheek; similar, but closer, on 
opercle; very few on pre-pectoral area; preventral widely exposed, more narrowly on 
post-ventral to anus. 
Ree Ava @. 28: 
The fins somewhat thickened, but scarcely fleshy, with coarse rays, somewhat 
roughened; dorsal and anal more rounded than in young; caudal somewhat broad- 
ened fanwise; pectoral broad, fan-shaped. 
