Cope. } O74 : [May 17, 
are sub-equal in length, and when extended reach nearly to the opercular 
border. A peculiarity of this species, which I do not find in the H. edenta- 
tus, is the porosity of the skin. A series of pores extends along each 
border of each myocomma, forming double rows, extending from the dorsal 
to the ventral line 3 mm. apart. The pores in each row are from one to 
two millimeters apart. 
The general color of this species is silvery, with the head and dorsal 
region lead colored. Total length M. .500; of head .108 ; to the line of the 
base of the anal .160 ; to base of caudal fin .435. 
Probably from Nauta. 
SILURID&. 
4. SorupiIM LIMA Bl., Schn. 
Coll. 1873—77. 
5. PLATYSTOMA FASCIATUM Linn. From Nauta, coll. 1873. 
I find the anal rays of the specimen to count II-9; Dr. Giinther gives 14. 
6. HEMISORUBIM PLATYRHYNCHUS Cuv. Val. 
Coll. 1877. 
7. PHRACTOCEPHALUS HEMLIOPTERUS Schn. 
Coll. 1877. 
8. PSEUDORHAMDIA PISCATRIX Cope, Proceed. Amer. Philos. Soc., 1870, 
p. 569. 
Coll. 1877. ~ 
9. PIMELODUS HUMILIS Gthr., Catal. Fishes, Brit. Mus. v 129. 
A specimen of about the size of those described by Dr. Giinther agrees 
with them very closely in all important respects. There are some differ- 
ences, however, which should be noted, especially since the typical speci - 
mens are said to have come from Venezuela. In the latter the distance 
between the dorsal fins is said to equal two-thirds the length of the adi- 
pose fin: in my specimen this space equals two-fifths the length of the adi- 
pose. The diameter of the eye in the former is described as one-half the 
width of the interorbital space ; in the Peruvian specimen, the diameter of 
the eye is a little more than one-third the same dimension. There is a 
dark cloud at the base of the rayed dorsal fin, whose superior border is 
abruptly contrasted with the paler color above it. The anterior part of 
caudal region is a little more elevated than the dorsal region. 
From Rioja, near Moyabamba, coll. of 1873. 
10. PrIMELODUS BATHYURUS, sp. nov. 
Head covered with thin skin, and not granular, but somewhat ridged above. 
Supraoccipital process long and narrow, not reaching the basal bone of the 
dorsal spine ; adipose fin contained 4.3 times in the length minus the caudal 
fin. The caudal portion of the fish is considerably deeper than the abdomi- 
nal, entering the length (less the caudal fin) six and three-tenth times. 
The head (to the opercular border) enters the same three and one-half 
times ; it is flat and rather elongate, and the mandible projects beyond the 
