Sketch of the Infusoria of the family Bacillaria, 329 
whose list of the species is given in this Journal, Vol. xxxrx, p. 
193; Blue Hill Pond, and various other localities in Maine, 
discovered by Dr. Jackson; Manchester, Spencer, Wrentham, 
Bridgewater, Andover, &c. in Massachusetts, discovered by Prof. 
Hitchcock, and Smithfield and other places in Rhode Island, dis- 
covered by Owen Mason, Esq. The largest and most conspicu- 
ous species from all these localities are Navicula viridis, Pl. 2, 
fig. 16, Navicula ? Pl. 2, fig. 23, Cocconema yy oe: 
fig. 11, Eunotia arcus, Pl. 2, fig. 26. With these occur various 
smaller species, and numerous siliceous spicule of fresh-water 
sponge, Pl. 3, fig. 18, @ to d, and other siliceous bodies of organic 
origin, such as the Amphidiscus rotula of Ehrenberg, Pl. 3, fig. 
20, and others whose nature is unknown, but which I suspect to 
be of vegetable origin, perhaps prickles of aquatic grasses. See 
Pl. 3, figs. 21, 22 and 23. 
The most interesting American deposit of fossil infusoria, is the 
“infusorial stratum” discovered by Prof. W. B. Rogers, of the 
University of Virginia. It is peculiarly interesting from its vast 
extent, the beauty of its species, and from its belonging to the 
marine tertiary formations. All other American fossil infusoria 
yet discovered are of fluviatile origin, and of the most recent date. 
I have already pointed out the striking correspondence between 
the fossils of the infusorial stratum of Virginia with those of Oran 
in Africa. This is shown by the occurrence of vast quantities of 
Various species of Coscinodiscus and Actinocyclus, with Gaillo- 
nella suleata? é&c. Believing that it will be of great interest to 
geologists both at home and abroad to trace out this correspond 
ence of the fossils of regions so far distant, and of beds which 
are at present referred to different epochs,* I have added to my 
plate 3d, a number of figures of siliceous bodies not before de- 
Scribed, found in the infusorial stratum of Virginia. The fol- 
lowing is a brief account of these bodies. ge 
In Pl. 3, fig. 24, a, 6, ¢, are shown different views of small 
siliceous bodies, which are quite frequent in the infusorial deposits 
both of Richmond and Rappahannock cliffs. ‘They consist of a 
concave rhomboidal body, formed of open work, or with large 
* Ehrenberg refers the infusorial conglomerates of Gran, &c. to the chalk for- 
mation, but Rozet considered them as tertiary deposits, and Prof. Rogers states 
that the beds discovered by him separate the miocene from t tertiary beds 
of Virginia. 
Vol. xu, No. 2—July-Sept. 1842. 42 
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