TASMANIAN DIATOMACK^E. 

 By F. E. Burbury. 



The swiftly flowiug South Esk River, coDfiued to its 

 narrow bed, in wliicli uauierous rock pools liave been worn , 

 the North Esk, a placid stream, subject to tidal influence for 

 some miles ; aud the Tamar River, formed by the junction 

 of these two, with a 40-miles course to the sea, and a 

 gradually increasing salinity, offer a specially favourable 

 habitat for various genera aud species of the Diatomacse, 

 and it is interesting to note the distribution of the genera — 

 in some cases indifferent to most severe changes in con- 

 ditious, in others suscej^tible to the slightest influences. 

 Thus Actinocyclus Barkleyi I have found at the First Basin, 

 a mile above the bridge, in fresh water, in company with 

 Synedra splendens and Nitzchia rif^jida and Nitzchia viridis. 

 The Actinocyclus is brought down into the slightly brackish 

 water of the Tamar basin, continues to thrive right down 

 the Tamar, is found again at George Town, and probably on 

 all coasts of Tasmania, as I have gatherings of it again from 

 Hobart. Not so, however, the synedras and nitzchias. 

 Nitzchia rigida at once gives place to varct. sigma and 

 it. sigma amphioxys, the slight, and it must be very slight, 

 amount of salt suiffices to bar the one species and aid the 

 other. The diatoms found in the purely fresh water of the 

 South Esk are those of a cosmopolitan character, being 

 probably all world-wide. In the North Esk, at that point 

 where the tidal influence ceases, two interesting forms are 

 met with — Euuotia transylvanica and a new Suirella of 

 large size, only heretofore met with in the bed of the Yarra 

 River. Coming down towards the wharves we find Hyalosira 

 Wliampoensis, «yn. with Triceratium javauicum, an extremely 

 interesting form. It is one of tlie three known species 

 belonging to the genera, and which usually inhabit tropical 

 seas. It is of interest to find it so far south. Some years 

 ago this form was found, and sent home to Kitton by Mr. 

 W. F. Petterd, and at this time was unknown excepit in 

 Java. It has, however, been since found in a fossil state in 

 Hungary. On the river flats by the Depot grounds are 

 found some fine specimens of the genera Suirella, viz., 

 Suirella splendida, Suirella robusta and spiralis, with a 

 newer species, rather rare, which also has been only hereto- 

 fore located in the Yarra. Here also the genera Coxinodixus 

 is represented by Eupodiscus commutatus. Some beautiful 

 Camplydiscus— Camplydixus echeneis and daemelianus, aud 

 an occasional valve of Triceratium Robertsiauum will reward 



