ANNOTATED LIST OF THE SPECIES 375 
Lake Titicaca and adjoining waters 
16064, 19, 30-80 mm., Rio Urubamba, Ureos, Eigenmann, December, 1918. 
16071, 6, 70-90 mm., R. Huatanay, Iscuchaca, Eigenmann, November, 1918. 
16073, 16, 38-84 mm., Rio de Langui, Eigenmann, November, 1918. 
16075, 8, 70-83 mm., Rio Huatanay, Cuzco valley, Eigenmann, December, 1918. 
16076, 14, 23-139 mm., Moho Bay, L. Titicaca, Allen, December, 1918. 
16092, 11, 48-83 mm., R. Porque, Tirapata, Allen, January, 1919. 
16095, 1, 109 mm., Lago Umayo, Allen, January, 1919. 
16098, 48, 32-103 mm., Lago Poopé, Bolivia, Allen, February, 1919. 
16099, many, 30-127 mm., Guaqui, Bolivia, Allen, January, 1919. 
16110, many, 49-102 mm., Chupa, R. de Chupa, Allen, January, 1919. 
16111, many, Rio de Chupa, 3 leagues up, Allen, January, 1919. 
16115, many, 32-105 mm., R. de Huancané, Allen, January, 1919. 
16124, many, Juliaca, R. de Lampa, bayoux, Allen, January, 1919. 
16125, 42, 27-110 mm., Juliaca, R. de Lampa, Allen, January, 1919. 
16127, 18, 42-82 mm., R. de Molino, near Juli, Allen, December, 1918. 
16128, 121, 25-80 mm., Azdngaro, R. de Azdngaro, Allen, January, 1919. 
A wide-spread species resembling O. agassizi/, although in younger stages 
usually darker, often much darker than any agassizii except the var. inornata, 
and similar in form; differing in the smaller mouth, striate scales, and flatter crown: 
not so evident in the young, the rotundity of the crown being doubtless sometimes 
a matter of trematode parasitism. The older specimens tend to be more com- 
pressed, with thickened scales more conspicuous on the shoulder, and not so 
widely distributed; head rather angulate. 
I found O. miilleri most abundant in and about the southern extremity of Lake 
Titicaca, less so along the western border or in Puno bay, but found in many 
localities about the upper end of the lake with its northern tributaries, and across 
the divide in the upper Urubamba valley. 
Known as the carache negro. 
Dorsal and ventral contours rather regularly convex, caudal peduncle com- 
pressed, but not very deep, widening at the caudal basis; crown slightly convex or 
flat; head roundly compressed at the opercle, its breadth 1.4 in its length; snout 
roundly pointed; head medium length, 3.6-3.8 in maturer specimens, and nearly 
equal to depth which is 3.3-3.4 in the length of the fish without the caudal; eye 
medium, 4.2 in the head, 2.0 in the interorbital space, just within the forward half 
of the head, shghtly oval, 1.0 in the snout; the supraorbital forming a slight bony 
eyebrow; opercular opening forming approximately a right angle. Larger miilleri 
with a distinct, but rounded, ridge along the upper margin of the opercle and to 
the end of the pectoral fin. 
Mouth rather small, oblique, gape a flattish crescent seen from front, becoming 
more horseshoe-shaped in the larger; lips present, not conspicuous; teeth rather 
few, dark, mostly in the first series. 
Scales mostly faintly striate, those of the crown, cheeks, opercle, shoulder 
thickened, cornified, smooth; few infraorbital scales, irregular; scales of cheek 
roughly three rows; prepectoral area finely scaled or desquamated. Preventral 
naked between bases of pectorals, thence narrowly to anus; some individuals with 
a bridge of fine scales before the anus; upper and lower surfaces of caudal peduncle 
with several rows of fine, irregular scales; fins closely invested with scales; the 
