Cope.] 692 [May 17, 
anal .028. Color silvery, with a broad bright silver lateral band, and no 
bright spots. 
Coll. 1874. 
90. TETRAGONOPTERUS IPANQUIANUS Cope, Proceed. Amer. Philos. Soc. 
1877, p. 28. Urubamba River ; elevation 11,500 feet. 
Coll. of 1877. 
91. STETHAPRION CHRYsEUM Cope, Proceed. Academy, Phila. 1872, p. 261. 
Coll. 1877. 
92. CHALCINUS CULTER Cope, l. c. 265. 
Coll. 1873. 
93. TRIPORTHEUS NEMATURUS Kner. 
Coll. 1872. 
94. SERRASALIMO IMMACULATUS 8p. nov. 
This species belongs to the restricted genus Serrasalmo. There are six pre- 
maxillary teeth, of which the third is much smaller than the others. Each 
tooth has a denticle at its posterior base, which in the case of the external 
tooth is longer horizontally than the principal cusp, and is not apiculate. 
There are seven in the lower jaw, of sub-equal size, each with a posterior 
basal denticle, except the anterior, which has two basal denticles. 
The form is discoid, the depth entering the length less the caudal fin 1.8 
times, and the length of the head entering the same three times. The 
dorsal and ventral outlines are equally convex, but the steeper slopes are 
opposite the anterior above, and the posterior below. Scales small 34-100- 
33. Radii; D.17; A. I. 32; V. 7, not reaching vent; P. 15, reaching base 
of ventrals. Spines 33-4. Gill rakers of first arch short, and with short 
apices. Diameter of eye entering length of head (including chin) five 
times; and nearly twice in the interorbital space measured over its con- 
‘ vexity. The origin of the dorsal fin is above the ventral, and equi-distant 
between the base of the superior marginal ray of the caudal fin and the pos- 
terior border of the orbit. The superior caudal rays are not so long as the 
inferior. Second sub-orbital bone as high as long. Muzzle a little longer 
than diameter of orbit. The color is silvery without distinct spots ; in cer- 
tain lights numerous small lead-colored spots may be detected on the dorsal 
region, extending half way down to the lateral line. Caudal and anal fin 
broadly black bordered ; no yellow band. Total length M. .190; of head 
.055; to line of dorsal fin .090 ; to line of anal .116 ; to basis of marginal 
caudal rays .161. 
This species is near the S. esopus Cope, but is readily distinguished by 
the much more numerous scales, and the longer muzzle. 
Coll. of 1877. 
95. METYNNIS LUNA, gen. et. sp. nov. 
Char. Gen. This is Myletes with an external horizontal cultriform 
spine at the base of the dorsal fin as in Serrasalmo and Stethaprion. The 
premaxillary teeth are in two series, and have an oblique, more or less in- 
