402 PROF. EHRENBERG ON FOSSIL INFUSORIA. 
the infusoria of which it consisted, that it is evident that the leaf-tri- 
poli sold at Berlin comes from Bilin in Bohemia, through Dresden. A 
similar stone to this is the Polirschiefer found at Planitz near Zwickau, 
if indeed the locality of the specimen examined by me be correct. But 
the Klebschiefer from Montmartre, which Klaproth has analysed, exhi- 
bited only doubtful traces of infusoria shields. The appearance of the 
fossil infusoria in the form of the Polirschiefer of Bilin is plainly of 
great importance to our further researches into geognostical rela- 
tions. In the same slate are found the impressions of an extinet fish, the 
Leuciscus papyraceus of Bronn, (according to Agassiz, ) and several im- 
pressions of plants, probably belonging to the tertiary formation. 
I had been inclined, even before these researches, to assign a great 
influence in the origin of the Raseneisen (bog-iron-ore) to an infusorium 
discovered by me in 1834, and of which I have, in April 1835, given an 
engraving in Plate X. of my Codex of Infusoria, under the name of 
Gaillonella ferruginea, which is perhaps the same as the Hygrocrocis 
ochracea of botanists. The minuteness of these corpuscles deterred me 
however from publishing this important circumstance; but since the 
discovery of so many and various shield-infusoria as stone masses, and 
since I have found that even the animalcule which almost entirely form 
the Polirschiefer of Bilin are also a species of the genus Gaillonella, I 
no longer hesitate to add this observation to the rest. That the for- 
mation of the Raseneisen, or of the Wiesenerz (meadow-earth), as 
a continual phenomenon excites great attention, and has given rise 
to many but not sufficiently explanatory theories, is well known. I 
have every spring observed in the marshes, particularly in the turf di- 
stricts about Berlin, large quantities of a substance of a very deep ochre 
yellow, sometimes passing into flesh red, often covering to a great ex- 
tent the bottom of the ditches from one to several feet deep, and much 
developed in small holes and in the footsteps of animals grazing. This 
mass is extremely delicate, and without any consistency, dividing itself 
at the least touch into an indefinite number of parts. Where it has 
become dry, after the evaporation of the water, it appears exactly like 
oxide of iron, for which it has been formerly often mistaken. We per- 
ceive however under the microscope, with a moderately high magnifying 
power, extremely slender articulated threads, the members of which 
measure only ;,/5, of a line, and in which the yellow colour is inherent. 
At the beginning of last summer I satisfied myself that these slender _ 
articulated threads do not lose their form in a strong red heat, but the 
colour changes to a red-brown, which is exactly that of iron-ochre. 
It was found that by the application of muriatic acid the colour was 
dissolved, without the articulated threads being changed: in the solu- 
tion precipitated iron was clearly visible. There is also one of the 
genus Gaillonella, very similar to the Bacillaria, but a very minute or- 
