602 SUBANTARCTIC ISLANDS OF NEW ZEALAND. [Crustacea. 



recent expeditions to southern seas ; and, as many of the forms found at these islands 

 are circumpolar in distribution, I have been in a position to correlate the various 

 reports, and to decide in certain cases where the same form has been described under 

 different names by different authors. In several groups of the Amphipoda the 

 multiplication of genera has been carried to what appears to me an unnecessary 

 degree, and characters have therefore been introduced into the generic diagnoses 

 which, in some cases at any rate, are subject to individual variation. While the 

 multiplication of species is bewildering enough, the unnecessary subdivision of genera 

 creates still greater confusion. 



As regards the geographical distribution of the species concerned, the results 

 seem to be somewhat important. Naturally, the chief interest attaches to the ter- 

 restrial and fresh-water forms of the Amphipoda and Isopoda. Of these, there are 

 in the islands three fresh-water and fourteen terrestrial species, including under the 

 latter the sand-hoppers found on the shores. Of the fresh-water species,* two occur 

 also in New Zealand ; one of these {Idotea lacustris) is also found in Tierra del 

 Fuego, the other {Chiltonia mihiwaka) is allied to species of the same genus 

 found in Australia and Tasmania, and is represented in South America by the closely 

 allied genus Hyalella. The third fresh-water species belongs to the genus Atyloides, 

 of which two species have been described from the fresh waters of Victoria, but 

 none as yet from the main islands of New Zealand. The genus as at present defined 

 contains both marine and fresh-water species. 



Of the fourteen terrestrial species, four belong to the genus Parorchestia, and 

 three of these are peculiar to the islands, the fourth species being found on the Snares 

 and in New Zealand (Stewart Island). Another closely allied species of this genus 

 is very abundant in New Zealand, but has not yet been recorded with certainty 

 from the subantarctic islands ; but, as I have explained below, the identification of 

 species in this genus is particularly difficult, and, in any case, we have here one 

 terrestrial genus common to New Zealand and the islands, and represented by 

 slightly different forms in the different islands. Of the remaining terrestrial 

 species, four are endemic, but are represented in the main islands of New 

 Zealand by closely allied species, and five others are identical with New Zealand 

 species ; consequently the connection between New Zealand and the islands lying 

 to the south of it is very close, and the existence of so many similar forms in the 

 two localities points, I think, undoubtedly to previous land connection. The 

 remaining terrestrial species occurs also in South America, but has not been 

 recorded from New Zealand. 



These terrestrial species, like the fresh-water ones, also show connection with 

 those of South America, Falkland Islands, and other subantarctic localities. One 

 species, Trichoniscus magellanicus, found in both Auckland and Campbell Islands, 

 is, I think, identical with one found in Tierra del Fuego and the Falkland Islands, and 

 is very closely related to T. verrucosus, which has recently been described by Budde- 

 Lund from the Crozets. Both these species, together with T. thomsoni (found in the 

 Auckland Islands and also in New Zealand) and with some other New Zealand species, 

 belong to a separate section of the genus Trichoniscus, confined in its distribution to 



* I liave not included Farorchestia tenuis (Dana) among the fresli-water species, as it can also live 

 in brackish or even in salt water. 



