ON AMERICAN IMFUSORIA. 
7 
tion by Professors Silliman^ Bailey and Hitchcock. The chief 
results of his examinations of American species are : 
1. In North and South America there occur not only living 
but fossil microscopic organisms_, forming strata geologically 
important, and very similar in their relations to the European. 
2. The American forms are for the most part similar to the 
European. 
3. One hundred and forty-three species are common to Eu- 
rope, and seventy-one (or one third), peculiar to America. 
4. Not one of the American infusorial deposits resembles in 
its elementary forms the chalk marl of the south of Europe. 
Nevertheless, there is found in the deposit near Spencer, Mass.^ 
the Rotalia glohulosa, which is decidedly peculiar to the writing 
chalk*. 
5. Most of the fossil deposits of North America are found in 
peat bogs, and contain forms of infusoria clearly referable to the 
brackish freshwater forms of the sea-coast, although some of 
them are at a distance from the sea. 
6. Catalogues of the American infusoria det(;rmined by Eh- 
renberg. 
* This statement was made before Prof. Ehrenberg was aware of the discovery 
made by Prof. W. B. Rogers, of the tertiary infusorial strata in Virginia. 1 have 
shown these strata to agree with those of Oran, &c., in containing immense mim- 
bers of the same species of Actinocyclus, Coscinodiscus, Dictyoclia, &c., which 
characterize the chalk marls of Oran, Caltisanetta, &c. Some of these species I 
have seen stiU hving in om' waters, not only on the sea-shore, as at Boston har- 
bour, but also sixty miles up the Hudson river. 
The occurrence of the marine Rotalia glohulosa, in the infusorial deposit of 
Spencer, an inland town of Massachusetts, would lead to curious inferences were 
the fact well estabUshed ; but having repeatedly examined specimens from that 
locality, and never having seen in them any but fluviatile organisms, I am inclined 
to think that a portion of chalk may have been accidentally mixed with Ehren- 
berg's specimens. — Note of the Editors of the American Journal cf Science. 
Some of the most common fossil species have been found still living so far 
west as Ouisconsin river. 
