JOURNAL 



OF THE 



ROYAL IICROSCOPICAL SOCIETY. 



DECEMBER 1881. 



TEANSACTIONS OF THE SOCIETY. 



XII. — Diatoms from Peruvian Guatio. 

 By the Eev. Lewis G. Mills, LL.D., F.K.M.S., &c. 



(Read 9ih November, 1881.) 

 Plate XI. 



Foe many years past it has been my custom, every winter, to make 

 a few large preparations of Peruvian guano, for the sake of obtaining 

 diatoms usually to be found in that deposit. I procured the 

 supplies of the material from extensive warehouses, and from time 

 to time, as samples of several importations. 



I have observed that within the last fifteen years, certain 

 changes have taken place as respects the diatoms to be found in 

 this guano, and my object in writing this short paper is to point 

 out a few of these changes, and to direct attention to a few remark- 

 able forms that have come under my notice when mounting the 

 slides from my many preparations. 



In the first place, however, I may state a few particulars in 

 which the guano of to-day agrees with that of fifteen years ago. 



The different forms of Cosoinodisous, common to the guano of 

 the past, remain constantly to be found in that of the present, and 

 in their usual abundance. The same remark apphes to the different 

 species of Adinopfychus. If there be any difference, it is that the 

 forms are now more frequent, and if anything, more perfect. 

 Endidya oceanica continues abundantly prevalent. A few ex- 

 amples of Aulacodiscus formosus may now be found in almost 

 every fair preparation. Auliscus joeruvianus which was not un- 

 usual in the past, is now so rare, that a single valve, from a large 

 quantity of material, would give me some surprise. I have not 

 had a specimen from the preparations of the last six years. Two 

 figures of this diatom were given by the late Dr. Greville in the 

 ' Trans. Micr. Soc. Lend.,' x. (1862). Auliscus ovalis (Arnott), for 

 a notice of which in Pritchard's work on Infusoria, Diatoms, &c., the 

 editor was indebted to Mr. F. Kitton, is now much more abundant 



Ser. 2.— Vol. I. 3 M 



