FOSSIL DIATOMACEE OF VIRGINIA. 97 
species of Campilodiscus, of which figures are given, Lign. 
111, figs. 1, 2. 
Some beds of porcelain-earth M. Ehrenberg found to be 
in a great measure made up of 
concentric articulated rings, entire 
and in fragments (see Lign. 6), 
which he believes to be bacilla- 
rie. 
Fosstiz DiaTOMACEZ OF THE — 
RICHMOND - HARTH ; VIRGINIA. — 
The town of Richmond, in Vir- 
ginia, is built on strata of sili- 
ceous marl of great extent, which 
have a total thickness, beneath 
and around the town, of more than twenty feet. These 
marls, whose organic composition was first detected by 
Professor W. B. Rogers, are referred by that eminent 
American geologist, to the older tertiary (eocene, or mrocene) 
formations. They occupy considerable districts, spreading 
out into sterile tracts along the flanks of the hills, their sili- 
ceous character rendering them unfavourable to vegetation. 
The investigations of Dr. Bailey have shown that the frus- 
tules so abundant in this earth, consist of several species 
of Navicula (Lign. 7, fig. 1, 1 a.), Galionella (Lign. 7, fig. 3, 
3 a.), Actinocyclus (Lign. 7, figs. 4, 5), &e. 
The most remarkable forms are disciform frustules, having 
their surfaces elaborately ornamented with hexagonal spots 
disposed in curves, and bearing some resemblance to the 
engine-turned case of a watch. ign. 7, fig. 2, is a small 
segment of a disc, very highly magnified. These frustules 
vary in size from 53, to +545 of an inch in diameter ; they 
are named Coscinodiscus (steve-like disc), and there are several 
species: one less richly sculptured, C. patina, is figured 
Iign. 7, fig. 6. Circular bodies, with five or six lines 
radiating from the centre to the circumference, like the 
VOL. I. H 
LicnNe 6: 
ORGANIC BoDIES IN PORCELAIN 
EartTH; highly magnified. 
