328 Sketch of the Infusoria of the family Bacillaria. 
Mr. Berkely has recently published (Ann. and Mag. Nat. Hist. 
Vol. 7, p. 449) some interesting observations, by which he ap- 
pears to have proved that the only species of this genus, the sin- 
gular G‘, paradorum, consists merely of rows of ova of some 
aquatic insect. He watched their development into larve. I 
have not seen American specimens. 
ScHIZONEMA. 
Envelope double, carapace siliceous, mantle tubular, tubes uni- 
ted in bundles, split in some places so as to appear branched, cor- 
puscles like those of Navicuua. 
No American species has yet been detected by me. 
End of the Bacillaria. 
It was my intention when I commenced the above sketch, to 
give in connection with it, an account of all the Amtrican local- 
ities of fossil infusoria, but further reflection has convinced me 
that this labor is unnecessary. All our fluviatile deposits of fossil 
infusoria, contain nearly the same species, and all these species 
are now living. From the great range which the living species 
have been shown to have in our country, there is great probabil- 
ity that all of the siliceous ones may be detected, if carefully 
sought for in any of the specimens of fresh-water infusorial de- 
posits. As for the localities at which these fossil infusoria occur, 
it does not appear that a particular enumeration is necessary: 
The living animals inhabit in great quantities almost every place 
where water remains several months in the year, their indestructi- 
ble shells are therefore to be found in greater or less quantity in 
the sedimentary deposits of all-our bogs, ponds and slow streams. 
These deposits are most remarkable beneath peat bogs, where 
they constitute strata many feet in thickness, and of great extent, 
often composed entirely of the siliceous carapaces of ani 
so minute that millions of them exist in a cubic inch. The 
“siliceous marl” which they form, is often so white and light 4s 
to be mistaken for magnesia, and Dr. Jackson states that it has 
_ actually been sold as such to apothecaries, who were much sur 
prised when informed by him that not a particle of magnesi# 
was present. 
_ Among the vast number of fluviatile localities now known, I 
think it necessary to allude only to the following, viz» West 
Point, from which specimens have been examined by Ehrenberg; 
