NATURAL SCIENCES OF PHILADELPHIA. 51 



Body ovate and compressed. Head conical in profile. Preoperculum ser- 

 rated behind, entire below, and armed at its angle 'with a large horizontal 

 spine. Operculum with its posterior angle subrotundate. Suborbital bones 

 serrated. Anterior dorsal with eight spines, the third of which is elongated. 

 Anal fin longer than the second dorsal, and furnished with three spines and 

 about thirteen rays. 



Type. Hypopterus macropterus Gitl. 

 Syn. Psammoperca macropterus Gtinther. 



b. * * * 

 Villiform teeth on the jaws, vomer and palate ; none on the tongue. 



Genus Percichthys Girard. 



Perca sp. Cuv. et Val., Jenyns. 



Percichthys sp. Girard, Proceedings of Academy of Natural Sciences of 

 Phiada., vol. vi. p. 197, 1854. 



Body and caudal peduncle elongated. Head conical in profile, with the 

 snout obtusely rounded or convex. Preoperculum serrated behind, armed 

 below with teeth directed forwards. Operculum armed with a single spine. 

 Preorbital bones scarcely serrated. Dorsal fins connected at the base by an 

 elevated membrane ; anterior with nine spines. Anal fin armed with three 

 spines. Branchiostegal membrane on each side with seven rays. 



This genus is composed of species peculiar to the fresh water streams of 

 the temperate transandean and the southern parts of South America. 



Type. Percichthys chilensis Girard. 



Genus Percosoma Gill. 



Percichthys sp. Girard, Gunther. 



Body elongated, but with the caudal peduncle quite short. Head conic in 

 profile, with the snout obtusely rounded. Lower jaw and suborbital bones 

 cavernous. Preoperculum serrated behind, armed below with recurved teeth. 

 Operculum armed with one spine. Dorsal fins joined at the base by the 

 elevated membrane ; anterior with nine or ten spines. Anal fin armed with 

 three spines. 



The branchiostegal membrane appears to have only six rays on each side. 



A single species is known to inhabit the fresh water streams of Chili. 



Type. Percosoma melanops Gill. 

 Syn. Percichthys melanops Girard. 



Genus Deuteropterus Gill. 



Perca sp. Cuv. et Vol. 

 Percichthys sp. Gwither. 



Body elongated. Head conical in profile. Preoperculum finely dentated 

 behind and beneath. Operculum terminating in a spine, above which a lobe 

 is present. Suborbital bone serrated. The anterior dorsal fin furnished with 

 nine spines ; the second long, with a spine and about seventeen rays. Anal 

 fin with three spines and about ten branched rays. 



Only one species of the genus is known ; its habitat is unknown. 



Type. Deuteropterus marginatus Gill. 

 Syn. Perca marginata Cuv. et Vol. 



b. * * * 



Head entirely covered with scales. Preoperculum mostly entire. Anterior 

 dorsal with about six rays. 



1861.] 



