376 FISHES OF WESTERN SOUTH AMERICA 
specialized scales of the shoulder more or less identifiable in young specimens 
down to 30 or 40 mm. 
As in other species, scales are more easily shed in early life and become more 
regular and more firm in later life, especially after reaching maturity. A few 
specimens were found to have the naked patches on either side of the back, de- 
scribed for several other species. In many streams most specimens, especially 
the young, were taken with fins mutilated. 
We t3 As 1: 
Dorsal base long, equal to its remoteness from the first caudal ray; its first 
rays short, increasing up to the eighth, the fin rounded posteriorly; the anal of 
similar form. Belonging to the group with thin, flexible, parchment-like fins, 
whose rays are light, the membrane dark between rays. In younger specimens 
the caudal is somewhat less elongate than in agassizii young, but similar in its 
being squarely truncate. 
Younger specimens up to about 50 mm. show considerable spotting, often with 
a lateral band, the irregular blotches falling into three longitudinal rows, the rows 
becoming concealed or broken in those of 60-80 mm. Sexually mature individuals 
were found at 90 mm. The older specimens become more compressed, and broader 
at the shoulder, and more uniformly colored with olivaceous or brown, some with 
fins clear, others not so dark, with four or five fine cross bars on the caudal. This 
series of color changes is very similar to that of O. agassizii. Also like the latter, 
specimens from muddy water tend to be much lighter, from saffron to light brown- 
Most specimens are bright silvery on the lower opercle, prepectoral, and pre- 
ventral areas. 
I found O. millert more abundant in lakes and less common in streams than 
O. agassizii. Also on more occasions I seem to have collected good series of all 
ages in a single locality. Are they less migratory in habit? 
486. ORESTIAS OWENIL Valenciennes 
Plate X XI, fig. 2 
Orestias owent? Cuvier and Valenciennes, 1846, Hist. Nat. Poiss., XVIII, 180; 
Garman, 1895, Mem. Mus. Comp. Zool., XIX, 152; 
Eigenmann, 1910, Rept. Princeton Univ. Exped. Patagonia, IIT, 461; 
Evermann and Radcliffe, 1917, Bull. U.S. Nat. Mus., no. 95, 42. 
Orestias agassizii Kigenmann and Kigenmann, 1891, Proc. U.S. Nat. Mus., XIV, 65. 
Lake Urcos and Cuzco valley, upper Urubamba 
15075, 8, 69-86 mm., Rio Guatanai, Cuzco, Eigenmann, December, 1918. 
16063, 19, 35-112 mm., Lake Urees, type locality, EKigenmann, December, 1918. 
Resembling O. miilleri, with similar smooth bucklers on the infraorbital, 
cheek, opercle, crown, and shoulder, but shorter and chubbier, more rounded 
about the anterior parts; chin more elevated; caudal peduncle moderate in depth, 
equal to the postorbital part of the head; like miller7 in color, light olivaceous above 
to light brown, yellowish below, all but the smallest uniformly colored. 
