SCHIZOPOD FROM TASMANIA. 301 



spring tides or after heavy rains, and afterwards found the same species further up the 

 lagoon where the water was quite fresh. My co-worker and friend, Dr. Chilton, has since 

 found the species in a mountain stream in the same neighbourhood at an elevation of 

 1200 feet. It is clear that in this instance this Isopod has within very recent times 

 made its way up the stream, where it is now thoroughly estabhshed. The same 

 species has been taken in the Straits of Magellan, and all the other numerous species of 

 the genus and family are marine with the exception of the Scandinavian Gbjptonotus 

 entomon. 



Leander fluviatilis, St/menosoma lacustris, and CalUophis fluviatilis occur in New 

 Zealand streams and lakes, and, though not found in the sea, are not uncommon in tidal 

 waters. Crangonyx compactus, Calliojmis siibteivaneus, ami Gammarusfrayills, found by 

 Dr. Chilton in the subterranean waters of Canterbury, and Pherusa cccrulea, found by 

 myself in a stream in the Old Man Range in Otago at an elevation of 3000 feet, are 

 species belonging to marine genera, which have most probably migrated from the sea by 

 gradual stages. I have myself taken Coroph'mm excavatum, Allorchestes recens, and a 

 species of Schizopod which I identify as Iltisldopsis incisa, Sars (origuially described 

 from a specimen obtained at the entrance of Port Phillip from a depth of 33 fathoms), 

 from the mouths of streams or lagoons where the water is frequently quite fresh. These 

 are a few examples, taken from instances occurring in New Zealand, of a gradual transi- 

 tion of marine into freshwater species, and of which similar examples could no doubt 

 be recorded from all other jmrts of the world. 



In such a manner most probably the ancestral forms of Anasjildes found their way 

 from the sea in Mesozoic times into the streams and lakes then occurring in Tasmania, 

 in which, to judge from its remarkable specialization, it has been isolated for a great 

 period of time. Its association with Phreatoicus australis and Niphargns montanus points 

 in the same direction. The former, as already stated, is an Isopod of a very old and 

 greatly generalized type. Its occurrence in two such isolated localities as Mt. Kosciusko 

 in New South Wales, a granitic mass of great antiquity, and Mt. Wellington in Tasmania, 

 and at a very considerable elevation m both, would appear to show that it has survived 

 thi'ough long periods of time ; coupled Avith which is the fact of the only allied species 

 being an eyeless form from the underground Avaters of Canterbury in the South Island of 

 New Zealand. 



The very vegetation on the summit of Mt. Wellington suggests the antiquity of the 

 region. Surrounding the locality in which Anaspides was found grow numerous forms 

 of plant-life characteristic of the Antarctic Plora of Tasmania, the Australian Alps, and 

 Isew Zealand, such as Abrotanellu, Doimtm, Carpha, Oreobolns, Uncinia, &c., so that 

 could one shut one's eyes to the Australian element which is so abundantly present, it 

 would not be difficult to imagine one's self on a mountain in the south portion of New 

 Zealand or on one of the peaty swamps of Stewart Island. 



These facts certainly give no direct testimony to the age of Anaspides, but they are 

 suggestive, and may enable us, when its development has been worked out and its own 

 distribution and that of its associated forms are better known, to arrive at some more 

 defluite conclusions on the subject. 



SECOND SERIES. — ZOOLOGY, VOL. YI. iO 



