noir on Microscopic Life. 307 
he thinks they must ha ged into the fine siliceous sand, 
which is present in these ochres. 
Maine.—Lists of the infusoria from two different de- 
posits discovered in 1838, near Blue-Hill Pond, in Maine, by Dr. 
Charles ‘I’. Jackson, are given. Both specimens were of a chalky 
whiteness, and all the “i with the exception of various Spon- 
giolites, (which are particularly abundant in one sample,) are 
decidedly fluviatile. Ehrenberg remarks on the difficulty of de- 
cision caused by the presence of these apparently marine spiculee 
of sponges, and says : 
_“ We may ask, if the formation is marine, why are no Coscinodisci, 
Actinocycli, &c. to be found? Perhaps it is a deposit from brackish 
water which in the neighborhood of the sea still contains some species 
of sponges.” 
As these Spongiolites suggest similar remarks by Ehrenberg 
With regard to various localities, we would state, that there can 
be no doubt that they are certainly of fresh-water origin, although 
some of them have much resemblance to some marine forms. 
The circumstances under which they occur in numerous locali- 
ties, hundreds of miles from the sea, and in the most recent de- 
posits of bogs and streams, leave no doubt of their fluviatile origin. 
. The notice of the species observed from Newfoundland, Lab- — 
tador, Kotzebue’s Sound, Iceland, and Spitzbergen, we are obli- 
ged to omit. 
In concluding this enumeration of American localities, Ehren- 
berg remarks: 
“That the extent and influence of the minuter American forms of ani- 
mal life now known to him does not terminate here. At the above men- 
tioned localities, the forms are chiefly siliceous, but microscopic calea- 
Teous organisms have also a most important development in America.” 
Allusion is then made by the author to the vast extent of the 
Cretaceous formations on the American continent, as shown by 
Dr. Morton’s Synopsis of the Cretaceous Group, and Von Buch’s 
splendid Memoir on the Petrifactions collected by Humboldt in 
America. Ehrenberg then observes : 
“Since the Academy was informed in 1838 that by a peculiar method 
of observation, it is possible to prove that all writing chalk and many 
compact calcareous rocks, result fromm the agglomeration of invisible 
Polythalamia, this method was applied in 1841 by Prof. Bailey to the 
Cretaceous rocks of North America, and the same results obtained.* 
Fe ended a 
Notice of Ehrenberg’: 
* See this Journal, Vol. x1, p. 213 and p. 400, © 
