A new Freshwater Amphipod from New Zealand. 423 



LXV. — A new Freshwater Amphipod from New Zealand. 

 By Charles Chilton, M.A., D.Sc, F.L.S. 



[Plate XVIII.] 



The Ampliipod described in this paper was first found some 

 years ago in a mountain stream on the slopes of Mount Mihi- 

 waka, near Port Chalmers, New Zealand, at a height of 

 about 1000 feet above sea-level. Afterwards I found it in 

 numerous other streams in the neighbourhood, and also at 

 Waitati, at various heights from about 200 feet above sea- 

 level up to an altitude of 1500 feet. Since then Mr. G. M. 

 Thomson tells me that his sons have collected it for him from 

 a small dam at a hillside stream at Hopehill, Taieri, from 

 spongy moss near the top of Mount Cargill, 2200 feet, and 

 from similar ground on the top of Swampy Hill, 2400 feet. 



Further investigation will probably show that it is widely 

 distributed in similar situations in the eastern parts of Otago 

 and perhaps elsewhere. 



I have usually found it in the damp moss &c. on stones and 

 boulders over which water trickles at the side of the stream, 

 and often in association with the freshwater Isopod Idotea 

 lacustriSj var. yS*. 



The occurrence of this Amphipod was briefly referred to 

 in my paper on the " Subterranean Crustacea of New 

 Zealand " f ; but no description has hitherto been published. 

 I refer it with some slight hesitation to the genus Hyalella, 

 numerous species of which are found in the fresh waters of 

 both North and South America. 



Hyalella mihiwaka^ sp. n. 

 (PI. XVIII. figs. 1-12.) 



Specific Description. — Male (fig. 1). Body stout and broad, 

 especially in the pereion, smooth. Eyes small, round. Side- 

 plates of the first four segments of the pereion much deeper 

 than their respective segments, the fourth much broader 

 than any of the preceding. First three segments of pleon 

 with the lower posterior angles nearly right-angled, very 

 slightly produced backwards. Telson simple, fairly large, 

 convex, subrectangular, posterior angles rounded, hind margin 

 very slightly produced in the middle. 



* See * Transactions New Zealand Institute,' xxiv. p. 263. 

 t Trans. Linn. Soc. 2iid ser., Zool. vol. vi. part 2, p. 254. 



