Art. XIII. — Phreatoicoides, a new Genus of Fresh-water 



Isopoda. 



By O. a. SAYCE. 

 (With Plates X., XI., XII.). 

 [Eead 14th September, 1899.] 



The specimen under consideration was found by the writer 

 during an excursion in the forest district of Thorpdale, Gipps- 

 land ; and was taken whilst searching logs of wood dragged from 

 out of a small tributary of the Narracan running through a 

 virgin fern-gully. The water was flowing somewhat rapidly, and 

 it is surprising that, being unable to swim, and also being devoid 

 of eyes, this animal should choose such a situation ; however I 

 only met with two or three specimens in the swift running water, 

 and these were taken from crevices within logs lying in the 

 water, and they had possibly been washed down from places 

 where the stream, through the damming back by fallen forest 

 debris, had widened out to form shallow gently running areas, for, 

 on searching in such localities, I found them somewhat numerous 

 and generally in little colonies. From one rotting tree-fern 

 trunk, lying in such a place, on cutting into the fibres, I took as 

 many as nine specimens within an area of six inches. 



On examination it has proved to be a form of considerable 

 biological interest, and I desire to record my debt of gratitude to 

 Professor Baldwin Spencer for aftbrding me laboratory facilities, 

 and for his personal interest and help in my work. 



From the following description it will be seen to be an Lsopod, 

 and, on account of fundamental differences in the pleon from any 

 recorded species, it appears necessary to form a new genus, for 

 which, because of its close affinity to Phreatoicus, Chilton,^ and 



1 In 1882 Dr. Chilton first described the frenus in the Trans. N.Z. Institute, vol. xv., p. 89, 

 In 1891 he described a N.S.W. species and considered the position of the genus in the 

 Records Aust. Museum Sydney, vol. i., p. 149, and in the Trans. Linn. Soc. London, May, 

 1894, he published an important paper in which he slif,'htly amended his generic descrip- 

 tion, and gave full particulars and drawings of the two New Zealand species, compared 

 them with their probable affinities, and gave other important details, as well as debated 

 some interesting biological questions connected with the Theory of Descent. 



