PERC0IDEJ2. 33 



One species may be supposed to travel round the Cape of Good Hope, viz., 

 Apogon rex-nmllorum, which exists in the Mediterranean, among the Canaries, in 

 the Indian Ocean, at the Marian Islands, New Guinea, and New Holland, but has 

 not hitherto been discovered in the American seas. It is, however, by no means 

 certain that a species which is found on both sides of a continent, or at a succession 

 of distant places, actually exists in the intermediate seas, or traverses them, for 

 Uranoscopus scaler is common to the Mediterranean and Indian Ocean, without 

 having been detected in the Atlantic ; and there are species of other families which 

 frequent the Mediterranean coasts of Egypt, as well as the Red Sea, though they 

 are unknown in other districts of the ocean. The range of the percoidecs, and of 

 many other Acanthopterygii, is much greater in the Indian Ocean and warmer 

 parts of the Pacific than in the Atlantic. Thus species which exist in the Red 

 Sea, at the Seychelle Islands, and the Mauritius, range by the Indian peninsula 

 and archipelago to New Guinea, the north coast of New Holland, and through the 

 Polynesian group to Otaheite, and even to the Sandwich Islands. A continuous 

 coast, or a chain of islands lying nearly in the direction of the zones of equal tem- 

 perature or parallels of latitude, seems to favour the spreading of a species over a 

 great extent of ocean. The shores of the Atlantic, which have a direction the reverse 

 of this, afford no such facilities to the migration of fish, the beds of sargasso, or 

 sea-weed that occur in the lower latitudes being but an imperfect substitute for 

 islands, and available to those fish only which feed on or near the surface. 



Having made these very general remarks on the diffusion of the genera, and on 

 the range of individual species, we have next briefly to notice the forms peculiar to 

 different quarters. Europe has five genera proper to itself, Aspro and Acerina, 

 inhabitants of fresh waters, and Pomatomus, Trachinus and Paralepis of the sea : 

 add to these Pentaceros, frequenting the Cape Verd Islands, and Apsihis the Cape 

 of Good Hope, and we have seven different forms, containing in the aggregate 

 fifteen species peculiar to the east side of the Atlantic. The genera proper to 

 North America all belong to the fresh waters, and are, Huro, Aphrodederus , 

 Bryttus, Centrarchus, and Pomotis ; while the Gulf of Mexico and Brazilian 

 seas contain Pinguipes and Percophis, in all nine forms and twenty-one species 

 peculiar to the American side of the Atlantic. Centropomus and Bovichtus are 

 proper to South America, but they occur in both oceans. Aplodactylus is pecu- 

 liar to the sea of Chili. Trichodon has been found in the Kamtschatdale Sea 

 only, and Niphon nowhere but in the sea of Japan. The Red Sea, Indian Ocean, 

 Polynesian and Australian seas, or the lands which they wash, contain twenty-three 

 percoid genera, not known to exist in the Atlantic or its arms, the Mediterranean, 



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