FISHES. 235 



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 Eio 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 PEROILIA, Girard. 



G-EN. CHAR. General physiognomy percoid ; body compressed. Two dorsal fins, contiguous at 

 their base, broadly sepa,rated 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. 



Stn. PerciUa, Grd. Proc. Acad. Nat. Sc. Philad. VII, 1854, 197. 



Obs. The genus PerciUa is a diminutive percoid, essentially characterized 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 Percichthys, 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. 



