Microscopic Animals of the Chalk-Formation. 399 



A seventh form, the fourth new one from Peru with which 

 we are acquainted, is a Cocconeis, found adhering to the 

 branchlets of the Polysiphonia. It has a strong resemblance 

 to C. undulala of the Baltic Sea, but is specifically different. 

 It may be named C. occanica. 



M. Ehrenberg also read a notice on the discovery of polir- 

 schiefer belonging to the black dusodile of Geistinger-Wald, 

 and on its nature as an infusorial slate. 



The author has shewn, partly before the Society of Na- 

 turalists at Berlin, and partly in the Annalea der Physik und 

 Chemie of 1839, that the yellow mineral species, known by the 

 name of dusodile, appears, on microscopic analysis, as a polir- 

 schiefer, composed of the shells or coverings of infusoria im- 

 pregnated with bitumen, and that what is called foliated and 

 papyraceous coal is nothing else than black dusodile. It was 

 therefore probable that in deposits of dusodile, particularly to- 

 wards the extremities, the polirschiefer would be found unal- 

 tered and not penetrated by the bitumen. The researches of 

 the author, in reference to this point, have not hitherto been 

 successful ; but a letter lately sent to him by M. Steininger 

 of Treves, the author of valuable works on the volcanos of 

 the Rhine, informs him that in a mine of Geistinger-Wald 

 he found, under lignite, a quantity of papyraceous coal, polir- 

 schiefer, and a kind of adhesive slate, and that he had al- 

 ready published this fact in 1821 in his work entitled Mate- 

 riaux pour servir a V Histoire des Volcans du Jihin, page 43. 

 The new researches of the author on infusorial slate have de- 

 termined M. Steininger to examine his assertions afresh, and 

 transmit specimens to Berlin. It follows from the examina- 

 tion of the latter, that there are polirschiefers adjoining the 

 dusodile of Geistinger-Wald (papyraceous coal) which have 

 produced the deposit of Infusoria, which, by the penetration 

 of bitumen, has been transformed into papyraceous coal or 

 black dusodile. 



The principal forms of the siliceous coverings which com- 

 pose the mass are, Gallionellae of very different sizes, perhaps 

 the different states of development of G. varians, among which 

 are deposited five species of Navicular, among others N.fulva, 

 and a very large pedicellated form, designated by the name of 



