INFUSORIA. 243 
GiifflONEMA. Envelope double; carapace siliceous; mantle tubular; tubes simple, often branched; 
corpuscles curved, resembling Cocconema in a tube. 
Mr. Berkely has recently published (Ann. and Mag. Nat. Hist. Vol. 7, p. 449) some inte¬ 
resting observations, by which he appears to have proved that the only species of this genus, 
the singular G. paradoocum, consists merely of rows of ova of some aquatic insect. He 
watched their development into larvae. 1 have not seen American specimens. 
ScHizoNEMA. Envelope double; carapace siliceous; mantle tubular; tubes united in bundles, split 
in some places so as to appear branched; corpuscles like those of Navicuia. 
No American species has yet been detected by me. 
It was my intention when I commenced the above sketch, to give, in connection with it, an 
account of all the American localities 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 probability that all the siliceous 
ones may be detected, if carefully sought for in any of the specimens of fresh-water infu¬ 
sorial deposits. 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 indestructible 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 animals so minute that millions of them exist in a cubic inch. The 
“ siliceous marl” which they form, is often so white and light as to be mistaken for magnesia, 
and Dr. Jackson states that it has actually been sold as such to apothecaries, who were much 
surprised when informed by him that not a particle of magnesia 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 Ehren- 
berg, whose list of the species is given in the American Journal of Science, Vol. 39, p. 193 ; 
Blue Hill pond, and various other localities in Maine, discovered by Dr. Jackson; Manches¬ 
ter, Spencer, Wrentham, Bridgewater, Andover, &c. in Massachusetts, discovered by Prof. 
Hitchcock; and Smithfield and other places in Rhode-Island, discovered by Owen Mason, Esq. 
The largest and most conspicuous species from all these localities are Navicula viridis, PI. 22, 
fig. 16, Navicula-? PI. 22, fig. 23, Cocconema-, PI, 41, Eunotia arcus, PI. 22, fig. 26. 
With these occur various smaller species, and numerous siliceous spiculae of fresh-water 
sponge, PI. 42, fig, 18, a to d, and other siliceous bodies of organic origin, such as the Am- 
phidiscus rotula of Ehrenberg, PI. 42, fig. 20, and others whose nature is unknown, but 
which I suspect to be of vegetable origin, perhaps prickles of aquatic grasses. (See PI. 42, 
figs. 21, 22 and 23.) 
The most interesting American deposit of fossil infusoria, is the “ infusorial stratum ” dis¬ 
covered by Prof. W. B. Rogers, of the University of Virginia. It is peculiarly interesting 
