BISHES. 231 



the two are to he 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 trucJia the anal is 

 said to he short, the caudal slightly rounded, the scales small, and the lateral line nearly 

 straight. Now, in Perciclitliys chilensis the anal is long and deep, the caudal is emarginated, 

 the scales are rather ahove than helow the middle size, and the lateral line forms quite a con- 

 spicuous curve along the dorsal region of the hody, heing straight only along the peduncle of 

 the tail. The formula of the fins of Fercha truclia, given hy Ciivier and Valenciennes, is as 

 follows : 



D. 9— 1 /l3; A. 3/ 10; C. IT; P. 14; V. l/s. 

 ■which, according to our method, will read thus : 



D X. 13 ; A III. 10 ; 0. I. 8. 7. I. ; V I. 5 ; P 14. 

 and compares hotter with the formula oi Perciclitliys chilensis given further on. The rudimentary 

 rays of the ujjper and lower lohe of the caudal are not enumerated by the French ichthyolo- 

 gists. It is to he regretted that their formula passed into the " Historia de Cliile" without 

 verification upon tlie specimens collected by Mr. Gay, on the ground merely that Cuvier pro- 

 nounced both species identical. It is true, they are called truclia both in Patagonia and Chile; 

 hut this is one instance in many of vernacular names similarly applied to more tlian 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 truclia of Chile. To this, however, I attach 

 no greater importance than it is worth. 



PEEOICHTHYS CHILENSIS, Girard. 

 Plate XXIX, Figs. 1—4. 



Spec. char. 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 of anal deeper than the height of second dorsal. Caudal 

 moderately emarginated posteriorly. Branchiostegals seven. G-round-color yellowish ; upper 

 regions covered with brownish or blackish diffused spots. 



Syn. Perclia trucha, GuicH, in Gay, Hist, de Chile, Zool. II, 1848, 146; Ictiol. Lam. I his. 

 fig. 1. 

 Percichtliys chilensis, Q-rd. Proc. Acad. Nat. Sc. Philad. VI, 1854, 197. 

 Truclia, vernacular. 



Descr. The body is subfusiform, compressed, and more elongated than in tlie 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 tlie 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 



