FRESHWATER CRUSTACEA OF TASMANIA. 



71 



Coast. The water in all these localities is very clear and cold. The species is at once 

 distinguished by its straight, unbent body and the dark brown pigmentation with 

 yellow markings. 



Genus Paranaspides, Smith. 



Paranaspides lacustris. 



Tbis species occurs only, so far as is known, in the littoral region of the Great Lake ; 

 the waters of this lake are never very clear, but always discoloured to a certain extent 

 with sand. P. lacustris is distinguished by its pale green transparent colour, finely 

 powdered with black dots, by its sharply bent body, and by the great size of the antennal 

 scales and tail-fan. 



Order ISOPODA. 

 Pamily Phreatoicid^e. 

 Genus Phreatoicus. 

 Chilton, Trans. Linn. Soc. Lond. ser. 2, Zool. vol. vi. (1894) p. 185. 



Remarks. — Besides the New Zealand species P. typicus and assimilis, P. australis 

 has been described (Chilton, Records of the Australian Museum, 1 & 2, 1890-95, p. 149) 

 from Mt. Kosciusko in Victoria and also recorded by Thomson (Proc. Roy. Soc. Tasmania, 

 1892, p. 76) from Mt. Wellington. Besides this a blind species, P. shephardi, has been 

 described by Sayce (Proc. Roy. Soc. Victoria, vol. xiii. 1900, p. 25) from Victoria. 



The other genera are Phreatoicokles (Sayce, Proc. Roy. Soc. Victoria, vol. xii. 1900, 

 p. 122) from Gippsland, Hyysometopus (Sayce, loc. cit. vol. xiv. p. 218) from burrows of 

 the land-crayfish Engceus in Tasmania, and Phreatoicopsis (Spencer & Hall, loc. cit. 

 vol. xix. 1896, p. 14), a large terrestrial form from Gippsland. 



As very little has been recorded of the habits or internal structure of these animals, 

 the following notes may be given : — Their movements are exceedingly sluggish, so that 

 when alive they are easily distinguished from the rapidly moving Amphipods, which in 

 external structure they so closely resemble. They appear to be entirely vegetable- 

 feeders, and subsist by passing a great quantity of vegetable mud, &c, through their 

 intestine, much in the same manner as an earthworm. This also appears to be the 

 habit in the land-form Phreatoicopsis. In specimens of this form which I dissected I 

 first noticed that the gut, which was full of earth, was provided with a highly developed 

 typhlosole or double fold, running its whole length, and quite unlike any structure met 

 with elsewhere among the Crustacea. The anterior portion of the gut, slit open along 

 the dorsal surface and displaying the gastric mill and the beginning of the double 

 typhlosole, is shown on PI. 12. fig. 13, while a diagrammatic transverse section (PI. 12. 

 fig. 12) shows the relation of the typhlosole to the wall of the alimentary canal. It is 

 evident that the vegetable mould, after being pounded up by the action of the ridges and 

 pads of the gastric mill, is passed underneath the typhlosolar flaps, which enormously 

 increase the area for absorption. A s imil ar typhlosole was found to exist in the various 



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