1869.] DR. A. GUNTHER ON NEW FISHES FROM PERU. 423 
The species of the Pig-family, as far as at present known, are in- 
fested by comparatively few parasites, which, when we bear in mind 
their uncleanly habits and mode of life, is rather singular. Our com- 
mon Pig has but one parasite, the Hematopinus urius of Nitzsch, or 
H, suis of Burmeister and Denny. 
It is an interesting fact that this genus Gyropus seems peculiarly 
American in distribution: the G. hispidus of the Ai, G. gracilis and 
G. ovalis of Cavia cobaya, and G. longicollis of Dasyprocta agree with 
G. dicotylis in being trom the western hemisphere. All the other 
Es are of minute size, the Gyropus ovalis being =", G. gracilis 
sig» G. longicollis } of a French line, G. hispidus about the same 
size. This species, being one-seventh of an inch in length, may fairly 
be reckoned as a giant in the genus. 
4. Descriptions of some Species of Fishes from the Peruvian 
Amazons. By Dr. Atperr Gtnruer, F.R.S., I.Z.8., &e. 
Some collections of fishes sent by Mr. E. Bartlett from the Upper 
Amazons were noticed in Ann. & Mag. Nat. Hist. 1866, xviii. p. 30, 
and in Proc. Zool. Soc. 1868, p. 229. In this paper I intend to de- 
scribe those species which were brought home by this traveller on his 
return to England, and which prove to be new. Unfortunately the 
specimens are not in so good a condition as those previously sent. 
The proportion of new forms is much less than we might have 
expected from those almost unexplored parts of the river Amazons, 
Mr. Bartlett’s collections having added only twenty-three species to 
this fauna. I may mention that the last collection contained also 
Sorubim lima (Bl. Schn.), Rhytiodus microlepis (Kner), and Myletes 
asterias (Miill.). 
MEGALOBRYCON, g. n. 
This genus is closely allied to Bryconops, from which it is techni- 
cally distinguished by the presence of a maxillary series of teeth. 
Dorsal aa placed in the middle of the length of the body, 1 imme- 
diately behind the ventrals. Anal long, Abdomen rounded in front 
of, and somewhat compressed behind the ventrals. Cleft of the 
mouth of moderate width. Teeth notched, in a triple series in the 
intermaxillary, and in a single in the maxillary and mandible ; no 
other teeth behind the mandibulary teeth or on the palate. Nostrils 
close-together.Gill-openings-wide. Scales of moderate size, with 
the free portion striated. 
MEGALOBRYCON CEPHALUS.- (Fig. 1, p. 424.) 
Dot. Av 24-26.8 t.lat..ca. 70. 
The height of the body is one-third of the total length (without 
caudal), the length of the head one-fourth. Intermaxillary in a 
triple series, those of the outer series bemg smallest, about twice as 
large as those of the maxillary ; the front mandibulary teeth largest. 
