FISHES. 31 
between the lateral line and the medial region of the belly. The scales decrease in size towards 
the occiput and the middle of the back, as well as towards the belly and throat. They are 
quite small on the cheeks, and so are those that are observed on the upper surface of the skull, 
on the suborbitals and maxillary. On the opercular-pieces they are nearly as large,as those on 
the flanks. - The lateral line, in which fifty-eight to sixty scales may be counted, forms an arch 
from the upper part of the opercular apparatus to nearly opposite the anterior margin of 
the second dorsal, where it reaches the middle of the flanks, hence straight to the base of 
the caudal. 
A dark blackish hue seems to pervade all the body and head, and yet the ground-color 
is whitish, mayhap sometimes yellowish. Innumerable black dots thickly spread over all the 
regions contribute to give to this fish its dark appearance. These dots being more particu- 
larly crowded upon the posterior third of the scales, it seems as if each scale bore a small spot 
or blotch. The upper surface of the head is uniformly dark brown or blackish. The sides of 
the head and opercular apparatus appear obsolately maculated. The inferior surface of the 
head, the throat, and the belly, exhibit more of the ground-color. The fins are all more or less 
yellowish, intensely dotted with blackish, so as to assume the general dark hue of the body 
itself, particularly the dorsals and caudal. 
This species inhabits the hydrographic basin of the Rio de Maypu. Specimens were procured 
from the neighborhood of Santiago. 
Plate XXX, fig. 1, represents Percichthys melanops, size of life. 
fig. 2 is an outline, viewed from above. 
fig. 3, a scale from the dorsal region. 
fig. 4, a scale from the lateral line. 
fig. 5, a scale from the abdominal region- 
Figs. 3, 4, and 5 are magnified. 
Genus PERCILIA, Girard. 
Gen. cHAR. General physiognomy percoid; body compressed. Two dorsal fins, contiguous at 
their base, broadly separated in their outline. Mouth rather small, or else of medium size; 
jaws subequal. Small conical teeth upon the maxillaries, and a few card-like ones on the front 
of vomer; none on the palatines. Tongue smooth. A few minute spines along the limb of 
preopercle. Opercle without any spines. External edge of suborbitals, sub and interopercle 
not crenated. Branchial aperture of either side continuous under the throat. Branchiostegals 
5 to 6 in number. Scales quite large and posteriorly ciliated. Cheeks and opercular apparatus 
scaly; top of head nearly smooth and nacked. Suborbitals and maxillary scaleless. Insertion 
of ventrals behind the base of pectorals. Caudal posteriorly “subcrescentic. 
Syn. Percilia, Gro. Proc. Acad. Nat. Sc. Philad. VII, 1854, 197. 
Oss. The genus Percilia is a diminutive percoid, essentially charac terized by a small mouth, 
the absence of palatine teeth, and an opercular apparatus nearly smooth, there being but a few 
minute needle-like spines along the limb of the preopercle. The maxillary teeth differ widely 
from those of Perca and Percichthys. The anal has three spiny rays, as in Perecichthys, but the 
position of the ventrals takes place as in Perca. Its general physiognomy resembles more that 
of Percichthys melanops than any other member of the family. The shape of the head and 
structure of the mouth denote an affinity with Percichthys, whilst the absence of scales on the 
upper surface of the head, the suborbitals, and the (upper) maxillary, remind us of similar traits 
in true Perca. 
