400 BOARD OF AGRICULTURE. 



of fresh water lacustrine forms for the most part the same as those 

 already given in the Maine deposits. Upon preparing a gathering, 

 however, from the living algas of the same pond, I at once noticed 

 the great abundance and large size of the pustules of Nitschia of 

 which not one fragment even could be detected in tlio deposit 

 below. Here then was certainly an instance in which one genus 

 at least, and that a large and well marked ©ne was entirely absent 

 from a fossil deposit, notwithstanding the fact that it is now and 

 has been for unknown years, growing in countless numbers in the 

 self-same pond, and gradually helping to form by its deposition a 

 new deposit, not three feet removed from the former ! Nor is this 

 a single instance. Not one of the common suZ^-peat deposits of the 

 country, such as those above mentioned, will be found to contain 

 any specimens of the genera "Nitschia" and " Synedra." One 

 deposit only, according to Dr. F. W. Lewis, and that ouer-lying the 

 peat is known to contain these genera. I have already mentioned 

 a Nitschia as occurring in the Beddington earth, and Mr. Edwards 

 of New York, has also alluded to one found in the Bemis lake, 

 (N. H.) earth, but these arc all isolated specimens, few in number, 

 and differing specifically from those which swarm in countless num- 

 bers in the same localities to-day. A similar fact has been noticed 

 by my father in regard to the great " infusorial deposits" of Ore- 

 gon and California. The forms obtained from the fresh-water ter- 

 tiary districts of those States were found to be wholly unlike the 

 recent infusoria from the Columbia river, and other existing streams, 

 and probably the same fact may be observed in all parts of the 

 country. As yet, however, this subject has received but little 

 attention. The great post-pliocene epoch to which most of these 

 deposits belong, has hitherto remained an unknown ground, with 

 little to mark its character beyond the confusion and tumult of the 

 great drift period. Probably' the " infusorial earths" were depos- 

 ited before as well as after, and perhaps during that period. The 

 diatomaceix! in which were found imbedded the bones of the Mas- 

 todon in Orange county, New York, in 1843, are exactly those 

 which characterize the greater part of the common sub-peat depos- 

 its, already referred to. The species which characterize that de- 

 posit may therefore be taken as the type of all similar deposits of 

 that age. Of the Miocene Tertiary beds of Diatoms, the Richmond 

 and Maryland earths afford undoubted examples, while to the 

 Eocene is referred by Ehrenberg the Aegina clay-marls and the 



