354 FISHES OF WESTERN SOUTH AMERICA 
KEY TO THE SPECIES OF THE GENUS ORESTIAS 
a. Scales nearly uniform throughout; venter scaled; small fishes 
b. Deep, compressed, pointed equally toward head and tail; greatest depth midway; lips 
hts) «hz Pe Rees crs Det shes 2 A Te a ne RE Teac ll IMENT BEd LN eM FP Bs mncae 
bb. Elongate; vertical chin, thin-lipped; caudal peduncle long, slender; deepest above pectoral 
AUTO eclectic et a EN eee ae? RADE EP? UA, ARUP ar oneal oh humboldtr 
aa. Seales enlarged and thickened cn anterior parts 
c. Scales of the head, opercle and shoulder enlarged, irregular, granular, especially in adults 
d. Fishes of elongate form; caudal peduncle slender 
e. Mouth, teeth, and eye large (6.6 in long head); mouth wide, oblique; 20 
scales in vertebral series...............0.0.0000ne sues ... cuvtert 
ee. Mouth smallish, nearly vertical; snout roundly pointed; head moderate, 
3.7-4.0; nape with low arch; granulations not extreme; scale rows Ir- 
repular= throuchouteylemo hie: ees ee ea eye eee, pentlandi 
dd. Fishes of short, robust form; nape arched; caudal peduncle short and deep 
f. Eye large, 4.8-4.5, elevated, supraorbital jutting over eye; snout short, 
less than eye; mouth horseshoe-shaped, vertical, thin; head angular; 
lateral angele acute; ‘crowm® flate.....e5..... snes ee eer luteus 
ff. Eye smaller, round; snout equal or exceeding eye; mouth oblique, fleshy; 
crown more or less convex; lateral angle broad 
e¢. Mouth upturned, back nearly straight; roundly compressed; caudal 
bases sexpandediy: seme) ee eee ee en: olivaceus 
ge. Head a wide cone, moderately rugged, pointed at chin; wide as 
deep; abruptly compressed caudally; high predorsal arch. . albus 
ec. Enlarged scales on anterior parts smooth and more or less polished, without granulations 
h. Seales of head and shoulder moderately thickened on small areas; little modifica- 
tion of general scale pattern 
i. Head wide and upturned, mouth superior, thin-lipped; dorsum straight; 
body wtapermne. from eeadh tos taille 0s eae eee stlustand 
ii. Body outlines rounded; caudal peduncle abruptly constricted far back on 
body; head pointed; mouth oblique, lips fleshy. ........... empyraeus 
hh. Scales of shoulder and head mostly thickened and cornified, forming a more or less 
dense armor of close-set bucklers 
j. Armor of anterior parts reaching to or beyond tip of pectoral fin; scales 
moderately specialized; predorsal slightly or moderately arched; scale- 
rows little disrupted or erowded; body not broadened at shoulder 
k. Small, elongate, scales mostly thin, little convex, deciduous. . elegans 
kk. Larger, deeper, wider fishes; scales smooth, more permanent in 
older specimens 
1. Arched predorsal, high above the end of opercle, tapering thence 
to tail; robust, not expanded; chin truncate; mouth and 
snout wide, lips thin; fins small, fleshy........ agassiziv 
ll. Predorsal arched equally with ventral profile; spindle-shaped 
forward from middle of body; chin roundly pointed, lips 
thick, preorbital portion of head long; tapering weakly 
Aovad, (VSL Gli JORMA BUA oe ease a wees anos Sue owentt 
jj. Body deep and wide at level of pectoral basis; thickly and densely armored; 
thickened and convex scales to beyond middle level of pectoral; chin 
vertical 
m. Elongate, mcderately deep; head in length 3.8; tapering gradually 
frcm the base of the pectoral fin to the tail............ miillert 
mm. Shorter form; deeper; head in length 3.3; depth in length 2.7-2.8 
n. Dorsal and anal fins oblique and caudal peduncle thin and 
shallow; its depth in its own length 1.3.......... Jussier 
nn. Tapering gradually shoulder to tail; caudal peduncle very 
deep, short, its depth equal toitslength.......... tschudit 
