FRESHWATER CRUSTACEA OF TASMANIA. G3 



the east and south the plateau is broken up and irregular, with extensive undulating 

 plains in the lowlands formed chiefly of the sandstones, but with occasional high 

 upstanding mountains of diabase, e. g. Ben Lomond in the north-east, Mt. Wellington 

 and the Harz Mountains in the south. The waters in this region, where they flow 

 chiefly over the diabase, are very pure and unclouded ; but where they flow over the 

 sandstones, especially in the valleys, they are yellow and cloudy. — (2) The North Coast. 

 The strip of the north coast is very varied geologically, with outcrops of granite and 

 basalt and rather extensive tertiary estuarine deposits, especially round the Tamar. — 

 (3) The West Coast. The west coast is a very mountainous and rugged district, the 

 mountains being formed of schists, and other metamorphic rocks of Archaean, Cambrian, 

 and Silurian age. The rainfall here is excessive (about 100 inches per annum) and the 

 mountains are clothed with forests of the evergreen beech {Fagus Canninghami), which 

 replaces Eucalypts, characteristic of the other districts. 



1. The Greenstone Plateau. 



The Great Lake. — At about 3000 ft. above sea-level is an extensive sheet of water, 

 90 miles in circumference, but nowhere deeper than 20 ft. The water is always some- 

 what discoloured by the sand stirred up by the waves. Round the edges are blocks of 

 greenstone with a good deal of weedy growth. The Crustacean fauna is very rich both 

 in point of variety of species and in number of individuals representing them. Almost 

 all the species are confined to the shallow littoral zone, the dredge in the deeper zones 

 bringing up nothing but fine mud without any life. In the littoral zone I found a new 

 genus of the Anaspidacea, named Paranaspides lacustris (Proc. R S. ser. B, vol. 80, 

 p. 470, 1908), a transparent green Ilysis-likc shrimp attaining an inch in length. 

 Crawling about in the weeds the very handsome Phreatoicus spinosus (PI. 12. fig. 7), a 

 new species, was abundant, and also the common P. auslralis (PI. 12. fig. 1). In the 

 deeper muddier zone the straw-coloured P. brevicaudatus, sp. n. (PI. 12. fig. 5), was 

 especially common. These three very distinct species were perhaps the commonest 

 Crustacea in the lake. Together with these were two abundant species of Amphipod, 

 Neoniphargus tasmanicus, sp. n., and Gammarus ripensis, sp. n. (PI. 14. figs. 5-8 and 

 PI. 14. figs. 23-26). 



The only native fish which inhabit the Great Lake are the little Galaxias, or native 

 " trout," G. auratus and G. truttaceus, which can never have been formidable enemies. 

 In the last 50 years the English Brown Trout has been introduced here and grows to an 

 enormous size in the lake (up to 25 lbs.). The trout examined by me all had very deep 

 pink flesh, and their stomachs were full of the above-mentioned Malacostraca, so there 

 is no doubt that they chiefly feed upon the Crustacea of the lake. Tow-netting during 

 the daytime produced very little result, but at night a rather poor quantity of plankton 

 was obtained consisting of the Cladoceran Bosmina brevirostris, sp. n. (PI. 16. fig. 1), the 

 first Bosmina to be taken in Australasia, and the common Cyclops albicans, sp. n. 

 (PI. 16. fig. 8). 



Lake Sorell. — This lake, at a rather low r er elevation than the Great Lake, is of a 



