328 
THE GEOLOGIST. 
FOREIGN CORRESPONDENCE. 
Communicated by Count Marschall. 
From the Proceedings of the Imjierial Academy of Sciences, Vienna, 
October, 1858. 
1. — Parasitic Algce in Shells. 
Certain channels met with in the shells of several Acephalous and 
Gasteropod mollusca have generally been considered to be nutritive 
channels, and to stand in organic connection with the pores of these 
shells. Professor Wedl after close examination of a number of re- 
cent and fossil specimens, has proved them to be accidental deteriora- 
tions of the shells, owing their origin to parasitic algse of most delicate 
structure. In the recent specimens these channels stand in com- 
munication with exiguovis cavities, including pedunculated cellules, 
filling up the channels themselves, and emitting a great number of 
lateral ramifications. The presence of Amylum in the nucleus, and in 
the cellules connected with it, manifests itself by the vivid brown tints 
they assume when brought in contact with diluted tincture of Iodine. 
The algse themselves have of course ceased to exist in fossil speci- 
mens, biit the characters of the channels in them, their irregular 
distribution, their connection with minute cavities, &c., are such that 
the identity of origin with those observed in living individuals can 
hardly be doubted. As far as investigations have hitherto proceeded, 
it may be inferred that fresh-water shells suffer more from these 
vegetable parasites than those of marine species. 
2. — Native Platina. 
Prince B. DemidofF has lately presented to the Imperial Mineralo- 
gical Museum a pepite of native Platina, weighing 11| lbs., found in 
his mines of Nishney Tagilsk, together with other large masses of 
the same metal, of which the most considerable have been very 
liberally oSered by the noble owner to the museums of Berlin and 
St. Petersburg. The Vienna pepite measures 5 inches in length, 4 
inches in breadth, and 3 inches in height. Its surface is covered 
with impressions similar to those on several pepites of native gold, 
indicating its origin within a fissure, and bearing some analogy (as 
the late P. Partch had remarked long ago) with the superficial im- 
pressions peculiar to meteoric iron. The impressions are partly 
filled with chromate of iron, which is generally associated with 
native Platina. 
