192 report— 1845. 



are too imperfectly known to enable us to ascertain how many of them range 

 to the other side of the great ocean. Is there a marked change either in 

 generic forms or species between the eastern limits of Polynesia and the 

 American coasts? 



The desultory observations I have thrown out respecting the distribution 

 of fish apply more particularly to the marine osseous fish, but those which 

 compose the sub-class of Cartilaginei have even a more extensive range. The 

 sharks of the China seas and of Australia are for the most part identical. 

 One of them, the Cestracion, has attracted the attention of geologists on ac- 

 count of the teeth of an ancient species having been found in European de- 

 posits, associated with fossil palms and other plants of the warmer regions. 

 But whatever inference may be drawn from the character of the plants, no 

 great reliance ought to be placed on the teeth of the Cestracion as an indi- 

 cation of the temperature when the deposit was made. The Australian 

 species, or one differing from it chiefly in colour and little in form, inhabits 

 likewise the seas of China and Japan ; and when deposits now forming are 

 revealed to the eyes of future geologists, its spoils will be found associated 

 with the Huon pines of Van Diemen's Land, the Eucalypti of New Holland, 

 the fern trees of New Zealand, or with the vegetation of the temperate parts 

 of Asia, according to the locality that is explored. 



With regard to freshwater fish, China agrees closely with the peninsula of 

 India in the generic forms, but not in species. It abounds with Cyprinidce, 

 Ophicephali and Siluridce. As in the distribution of marine fish the inter- 

 position of a continent stretching from the tropics far into the temperate or 

 colder parts of the ocean separates different ichthyological groups ; so with 

 respect to the freshwater species, the intrusion of arms of the sea running 

 far to the northwards, or the interposition of a lofty mountain chain, effects the 

 same thing. The freshwater fish of the Cape of Good Hope, and the South 

 American ones are different from those of India and China. The remarkable 

 mailed Siluroids of intertropical America are unlike any freshwater fish of 

 Africa or Asia, while the Ophicephali are almost exclusively Asiatic ; a genus 

 of the same family being found at the Cape of Good Hope but none in Ame- 

 rica. The Cyprinidce have been said to be wanting in Polynesia and Au- 

 stralia. In the coral islands of Polynesia their absence is clearly owing to 

 the want of lakes or rivers, and of Australia it may be said that the rivers 

 have not been sufficiently explored. They exist in the larger islands of the 

 Javan chain, and it is likely that the same species will hereafter be detected 

 in the northern parts of Australia. And the Cyprinoid family is not alto- 

 gether unknown in Australia. A curious marine Cyprinoid, the Rhynchana 

 greyi (Ichth. of Voy. of Erebus and Terror), is not rare in the seas of New 

 Zealand and South Australia. It has been a prevalent opinion that the Cy- 

 prinidce are exclusively freshwater fish, but the Catastomi of North America 

 frequent the estuaries of the rivers which fall into the Arctic sea, living indif- 

 ferently in the salt and fresh water, and thriving w r herever they find proper 

 food. The anadromous Percoids differ very slightly in form from others that 

 are purely inhabitants of fresh waters ; and many examples of the same kind 

 might be adduced from among the marine fish *. The common anadromous 

 salmon (Salmo salar) does not descend beyond the 41st degree of latitude on 

 the eastern coast of America, and it is probably restrained within similar bounds 

 on the eastern coast of Asia, for we find no representations of it among the 



* In the genera Ambassis and Apogon, there are species truly marine, with others closely 

 resembling them, that inhabit fresh waters and even thermal springs of high temperature. 

 Most of the Corcgoni pass their whole lives in inland waters, but many individuals, earned 

 down to the sea by river floods, live and thrive in the brackish or salt waters of the estuaries : 

 and the brackish lagoons of Port Essington on the north coast of Australia furnish full-grown 

 examples of Carangi, Mesopriones, and other fish considered to be purely marine. 



