454 Evolution and Distribution of Fishes 



waters; and, in listing twenty species, he remarks regarding 

 the genus that: "It Is rare in rivers of N. S. Wales, more 

 abundant In Victoria, still more so in Tasmania and N. 

 Zealand." But it Is at least likely — almost assured — that 

 both species originally occurred, as do the others of the 

 genus, at relatively low levels, and that the regions now 

 Inhabited by them were subjected to an upthrow or to a 

 gradual elevation of at least 2000 feet to 3000 feet, during 

 the late Miocene or early Pliocene when extensive terrene 

 disturbances took place. The passage of one or two into 

 a brakish and later marine environment, Is in keeping with 

 the origin of marine teleosts In general. 



In this connection loose and contradictory statements 

 have at times been made regarding the group of fishes now 

 under discussion, that might tend to obscure exact Issues. 

 Thus In "Fishes of New Zealand" (2^/: 61) Hutton, in 

 listing the only other species and genus — Neochanna apoda 

 — of the Galaxidae, calls It appropriately "Mud Fish," 

 but gives as Its locality "West Coast of North and South 

 Island." Hector, in describing "Edible Fishes" In the 

 same publication, shows that it is not only a mud or swamp 

 fish, but that alike over the north and south island "wherever 

 this curious fish has been found it is always buried in the 

 mud, and It Is singular that It should have such a wide 

 distribution, if It does not also exist in the neighboring 

 rivers." He quotes Giinther's opinion also that it is "a 

 degraded form of the more highly developed type of 

 Galaxias," being devoid of ventral fins, and showing a 

 rudimentary condition of the eyes. Both structural features 

 are evidently the result of the slow proenvironal response 

 of the species to its environal habitat. But like the other 

 species of Galaxias It Is truly a freshwater type. 



But probably about the period that species of Galaxias 

 were being raised into high elevations, alike in east Aus- 

 tralia and In Tierra del Fuego, the same process was pro- 

 ceding along the Andes, and so caused separation and ele- 

 vation of a species of Trichomycteriis that is now found In 

 Lake Titlcaca, from other species of the genus that were 

 left at varying elevations along the Andes, from Caracas 

 to S. Chile. Other fishes of Lake Titlcaca have been al- 



