Chilton. — The Fresh-water Amphipoda of New Zealand. 53 



up on the shore of Mason Bay, on the west of Stewart Island. This last 

 occurrence has been difficult to account for, owing to the absence of volcanic 

 rocks on the island, but if there is any extent of submerged volcanic land 

 to the westward the powerful currents and heavy seas could easily explain 

 the presence of scoriaceous material on the west coast of Stewart Island. 



The Solanders are undoubtedly the remnant of a volcanic cone of 

 probable recent date, a large part having been removed by powerful marine 

 erosion, or been buried under the sea on the land in the locality sinking. 

 There is evidence both from the Sounds of Otago on the one hand, and from 

 the drowned valleys of Stewart Island on the other, that the land was 

 formerly higher, and is now depressed much below its former level. There 

 is also evidence of a very recent elevation. It is possible that the sub- 

 mergence of a large block of land to the south and south-west of New 

 Zealand was connected not only with the formation of the valleys and fiords 

 of western Otago, but also with the volcanic outbursts at the Solanders. 

 Foundered areas, as it has been pointed out, are associated with fractures 

 in the neighbouring crust, which may determine the direction of valleys 

 to a certain extent, and thus affect the initial stages in the formation of 

 fiords ; and fractures are no doubt also intimately connected with volcanic 

 action. Their occurrence together in this case may be only a coincidence, 

 and not a different surface manifestation of the same deep-seated cause. 



Art. XIII. — The Fresh-water Amphipoda of New Zealand. 



By Charles Chilton, M.A., D.Sc. F.L.S., Professor of Biology, Canterbury 



College, N.Z. 



[Bead before the Philosophical Institute of Canterbury, 4th November, 1908.] 



The immediate cause of this paper was the discovery in February, 1908, 

 of a fresh-water gammarid at Rona Bay, Wellington Harbour, which, on 

 examination, proved to be the same as Phreafogammarus jnojnnquus, a species 

 described in 1907 from a single specimen collected by Mr. Crosby Smith 

 on Mount Anglem, Stewart Island. This species was of special interest 

 as the first species of Phreatoyammarus to be recorded from the surface 

 waters of New Zealand, and owing to its near relationship to P. fragilis, 

 a species inhabiting the underground waters of the Canterbury Plains. 

 During the last few years, too, several facts referring to the other fresh- 

 water Amphipoda have been collected, and it seems desirable to gather 

 them together here. This group of the Crustacea possesses considerable 

 interest from the point of view of geographical distribution, and for this 

 reason a paper on the subject was commenced and partly written out about 

 fifteen years ago, but was then left unfinished owing to want of knowledge 

 of the fresh-water Amphipoda of Australia and elsewhere. Since then many 

 of the gaps have been filled up, and, though our knowledge is still far from 

 complete, some comparison of the fresh-water Amphipoda of New Zealand 

 with those of other countries is now possible. 



