TASMANIAN DIATOMACE^. 



By F, E. Bukbury. 



The swiftly flowing South Esk River, confiued to its 

 narrow bed, in which numerous rock pools have been worn , 

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

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

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

 gradually increasing salinity, offer a specially favourable 

 habitat for various genera and 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 susceptible 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 rigida 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 suffices 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 cosmoijolitan character, being 

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

 where the tidal influence ceases, two interesting forms are 

 met with — Eunotia 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 

 Whami^oensis, syn. with Trieeratium javauicum, an extremely 

 interesting form. It is one of the three known species 

 belonging to the genera, and which usually inhabit trojncal 

 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 except 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 sj^iralis, 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 daenieliauus, and 

 an occasional valve of Trieeratium Robertsiauum will reward 



