ANNOTATED LIST OF THE SPECIES 367 
or albus at first, and a considerable metamorphosis must be assumed between the 
stages here represented. They cast some doubt upon the validity, otherwise satis- 
factory, of the assortments of genes by which my two main branches of the genus 
are separated. 
Dorsal profile very slightly and uniformly elevated from snout to dorsal fin, 
thence very slightly concave; ventral profile very convex from the elevated mouth 
to the throat, thence slightly convex, anal basis a little oblique; general form 
tapering from head to tail; caudal peduncle thinly compressed, rather short, not 
deep nor expanded at the caudal basis; width at opercle moderate, 1.6 in the depth, 
which is equal to the length of the head and 3.3 in the length to the base of the 
caudal. Head much shorter than in olivaceus, 3.6 compared to 3.0. 
Kye rather small, circular, elevated, 5.0 in the head, 2.0 in the interorbital 
space; mouth very superior, rather small, less than interorbital space; lips thin, teeth 
in one weak series in each jaw. 
Scales striate, infraorbital sparsely scaled, scales of shoulder, cheek, and opercle 
only moderately thickened, lustrous; 15 scales in vertebral series; those of prepec- 
toral area sparse, but postpectoral well scaled downward to a narrow naked band 
on the belly. 
ID), Wake ANS leg EX PAO): 
Origin of dorsal midway from occiput to caudal basis; fins small, thin, mem- 
branous, not roughened or fleshy. 
Light gray to light brown above; whitish ventrally; conspicuously yellow on 
opercle; numerous small patches of minute chromatophores on the body; fins with 
staggered rows of fine, elongate punctulations, more regular on caudal, united into 
larger spots on the dorsal. 
The smaller specimens, paratypes, were at first mistaken for luteus or albus, 
being more convex on the back, but are of more elongate form, and begin to show 
the smooth-scaled epaulettes of the miilleri group at the age when albus and luteus 
are taking on the granulate form of scale. Differing from albus of equal size in 
the color and much more compressed rather than rounded; unlike luteus in the 
less pointed lateral angle, more pointed and not truncate head, oblique gape, 
smaller eye, more elongate caudal peduncle. 
The name silustani is that of the nearby Inca ruin on the shore of Lake Umayo, 
overlooking the weedy habitat from which the species was collected. 
482. ORESTIAS EMPYRAEUS Allen, sp. nov. 
Plate XX, fig. 2 
Central Peru; upland pampas, upper Mantaro 
15232, many, 20-115 mm., Huancayo, Eigenmann, September, 1918. 
15233, many, Jauja, Peru, Eigenmann, September, 1918. 
15234, many, Pachachaca, Eigenmann, September, 1918. 
15235, 1,35 mm., R. Mantaro, Eigenmann and Allen, September, 1918. 
15236, many, 25-63 mm., Zigzag, Allen, September, 1918. 
15237, 22, 27-94 mm., Tilarnioc, Kigenmann, September, 1918. 
15238, many, 16-150 mm., Lago Chinchaycocha, Allen, October, 1918. 
