J. Hall on the Genus Archimedes or Fenestella. 203 
_ Ina “Report upon the Mineral Resources of the Illinois Central Rail- 
road, by J. W. Foster,” published in 1856, a section similar to the one 
friends, has had occasion ne regret “that ‘Dr. Norwood has not long since 
published some portion of the accumulated facts of many years of inves- 
igati 
Although aware for several years of this relative position of the lower 
and the coal canis yet I was never fully impressed with the 
high interest fediee importance of the matter, until I had carefully followed 
out the successive sidintated of the Carboniferous limestone series. Dis- 
claiming any desire to appropriate the discoveries of others, the writer has 
presented in the preceding paper the facts that came under his own 
siren, and the conclusions which seemed es deducible 
eref 
aiaomlage th a valuable aid rendered to me y Mr. A. H. Wo my 
fi Tocalitics of the earboniferous Jimestones in the sien val- 
i y enabled me to accomplish my investigations in much less time and 
been ab. 
4 asingle season. Wee explored together these formations as far as the 
mouth of the Ohio, after which Mr. Worthen carried on, under my direc- 
tion, the observations through Tennessee and Alabama, with a view to 
recognition of “as groups established in the investigations in rege: 
linois and Missour 
t 
har. 2 € 8 Me cae upon the Genus Archimedes or Fe 
oe Cron Lamestones of the Mississippi Vali: ‘ 
THE term Archimedes has long been in use among American 
Seologists, and is the generic name given by Lesueur toa Bryo 
zoan, which co consists of broad reticulate expansions, 
at their base, and spirally arranged around an elongated axis or 
stem, or, perhaps more properly the thickened base forms the 
axis. The axis is solid or arly cellular in its interior 
re, — ftom anded portions have the general character of 
Fenestella wp e lower or external side, while the upper or 
inner side j me oi: like manner celluliferous. The cell are cyl- 
indrical with circular or sub-circular mouths, arranged a 
the ‘evr agg in two or more rows; the branches are rounded or 
ie apa 8 transverse processes, 
* orb gular inters 
