NATURAL SCIENCES OF PHILADELPHIA. 47 



ters in many respects correspond to those of the first group of the Percoids of 

 Giinther, called by him Percina, but several genera are introduced into the 

 latter which destroy the natural character of the group. The genus Parala- 

 brax of Girard belongs more properly to the Serranince, as does also Etelii 

 of Cuvier and Valenciennes. On the systematic value of Acerince and Aspru. 

 we have already remarked. Boleosoma and Pileoma of Dekay are certainly not 

 natural members of the Percince, nor can they even be properly regarded as 

 belonging to the same family ; they are more nearly allied to the Gobioidg. 

 Finally, Enoplosus of Cuvier appears to be the type of a distinct subfamily. 



The Percina, although represented by many generic forms, are not numer- 

 ous in species. Many of them are found in fresh water, and probably all of 

 them ascend rivers for a short distance, at some period of the year or are 

 found at their mouths. 



The following scheme is supposed to show nearly the natural order and 

 characters of the known genera. As several of them have not been seen by 

 us, we remain in doubt as to their natural position. 



S i. 



Intermaxillary and palatine bones provided with some large teeth, arranged 

 in rows ; rest of the teeth villiform. Tongue toothless. 



Genus Stizostedion (Raf.) Girard. 



Les Sandres Cuv., Regne Animal, ed. i. vol. ii. p. 294, . . . 1817. 

 Stizostedion Raf., Ichthyologia Ohiensis, p. 23, . . , . . 1820. 



Lucioperca Cuv. et Val., Hist. Nat. des Poissons, vol. ii. p. 110, . 1828. 

 Sandrus Stark, Elements of Natural History, vol. i. p. 465, . . . 1828. 



Body slender, elongate-fusiform, covered with scales arranged in oblique 

 rows. Head semiconical, quite broad, with the cheeks and opercula generally 

 covered with scales ; isolated patches of scales on the sides of the posterior 

 part of the head ; rest of the head covered with a naked skin. Preoperculum 

 serrated ; operculum armed with from one to five spines. Dorsal fins two : 

 the first supported by from twelve to fifteen spines. 



This genus is peculiar to the fresh water streams, rivers and lakes of North 

 America and Europe. 



II- 



Intermaxillary, vomerine and palatine bones provided only with villiform 

 teeth. 



A. 

 Pseudobranchiae present. 



a. 



Head with its superior surface scaleless, or only with two scaly areas on 

 each side of the posterior part. Anterior dorsal fin provided with from seven 

 to fifteen spines. Tongue without teeth. 



* 



Lateral line linear, ceasing at the base of the caudal fin. 



Genus Perca Linn., Cuv. 



Perca sp. Linn., Systema Natura?. 



Perca sp. Cuv. et Val., Hist. Nat. des Poissons, vol. ii. 



Perca Giinther, Catalogue of the Acanthopterygian Fish, &c, vol. i. p. 62. 



Body elongate-fusiform. Head conical in profile, covered on the cheeks 

 and preoperculum, suboperculum and upper part of the operculum with 

 cycloid scales of moderate size. Operculum generally naked and radiatedly 

 striated. Preoperculum with its anterior margin well defined and entire, and 



1861.J 



