FISHES. Pt 
the two are to be found in the structure of the anal, dorsal, and pectoral fins, the shape of the 
caudal, the size of the scales, and the course of the lateral line. In Perca trucha the anal is 
said to be short, the caudal slightly rounded, the scales small, and the lateral line nearly 
straight. Now, in Percichthys chilensis the anal is long and deep, the caudal is emarginated, 
the scales are rather above than below the middle size, and the lateral line forms quite a con- 
spicuous curve along the dorsal region of the body, being straight only along the peduncle of 
the tail. The formula of the fins of Percha trucha, given by Cuvier and Valenciennes, is as 
follows : 
Oe ys 1/13; A. 3/10; CO. 17; P. 14; V. 1/5. 
which, according to our method, will read thus: 
DRE 3 AGO Onna ie la Oe Velma 14 
and compares better with the formula of Percichthys chilensis given further on. The rudimentary 
rays of the upper and lower lobe of the caudal are not enumerated by the French ichthyolo- 
gists. Itis to be regretted that their formula passed into the ‘‘ Historia de Chile’’ without 
verification upon the specimens collected by Mr. Gay, on the ground merely that Cuvier pro- 
nounced both species identical. It is true, they are called ¢ruwcha both in Patagonia and Chile; 
but this is one instance in many of vernacular names similarly applied to more than one zoologi- 
cal species. 
None of the specimens which came under my observation did exhibit roundish black spots 
as figured in the ‘‘ Historia de Chile,’’ which may after all become another distinguishing 
feature between the trucha of Patagonia and the trucha of Chile. To this, however, I attach 
no greater importance than it is worth. 
PERCICHTHYS CHILENSIS, Girard. 
Pirate XXIX, Figs. 1—4. 
Spec. car. Snout subconical, obtuse anteriorly, and slightly overlapping the lower jaw. 
Mouth well developed. Posterior extremity of upper maxillary fetching the vertical of centre 
of pupil. Limb of preopercle conspicuously serrated; exterior margin of sub and interopercle 
inconspicuously so. Soft portion gf anal deeper than the height of second dorsal. Caudal 
moderately emarginated posteriorly. Branchiostegals seven. Ground-color yellowish; upper 
regions covered with brownish or blackish diffused spots. 
Syn. Percha trucha, Guicu, in Gay, Hist. de Chile, Zool. II, 1848, 146; Ictiol. Lam. I bis. 
fig. 1. 
Percichthys chilensis, Grp, Proc. Acad. Nat. Sc. Philad. VI, 1854, 197. 
Trucha, vernacular. 
Descr. The body is subfusiform, compressed, and more elongated than in the common perch of 
the United States. The greatest depth, which corresponds to the origin of the first dorsal fin, 
is contained four times and a half in the total length; whilst the least depth, taken on the 
peduncle of the tail, enters in the same length nearly ten times. The back is uniformly 
arched from the nape to the termination of the second dorsal. The peduncle of the tail con- 
stitutes almost the fifth of the whole length. The abdominal outline is convex from the throat 
to the end of the anal fins. The greatest thickness is a little more than half of the depth; 
the thickness of the peduncle of the tail is exactly the half of its depth. The head, which is 
subconical, is continuous with both the dorsal and abdominal outlines, if we except a very 
slight depression upon the vertex. It forms about the fourth of the entire length. The 
