196 L. Lesquereux on the Coal Formations of the United States. 
abruptly eut and hollow, like the mouth of a thick shelled mol- 
usc. It is finely striated across; and under a stroeg lens looks 
like a beautiful small Ammonites. From numerous cross sections 
of good specimens of this small body, I must admit, contrary to 
the opinions of the learned European authors who have studied 
it, that it is a true shell, most probably a species of freshwater 
mollusc. Internally it is hollow, with a hard, thick, parietal 
substance, generally of lighter color than the shale. It is true 
that it is often found within the carbonaceous matter of the 
leaves and of the stems, and thus would appear to have lived 
within the substance or under the epidermis of tlie plants like 
some Hypoaxylec. But at Colchester, at least, it is still oftener 
found within the naked substance of the shales. Moreover if 
it was a shell living on the stems and leaves of the coal, it has 
been of course imbedded by compression as well in the softened 
woody and carbonaceous matter of the plants as in the soft clay. 
Germar has already remarked that he found it on shales, without 
any apparent connection with vegetable substance. But he 
supposes the possibility of the destruction of all vegetable sub- 
stance, except that of this small fungus; a supposition which ap- 
pears somewhat extraordinary. The presence of fresh water 
shells in the bogs of the coal can not be doubted after the re- 
markable discovery by Prof. Dawson of a fresh water Pupa in 
the coal fields of Nova Scotia.* And the scarcity of these 
molluscans in the coal measures is in accordance with what we 
see on the peat bogs of our time, where the number of fresh 
water shells is extremely limited. I can not but say again how 
difficult and hazardous it is to determine such small bodies _ 
"attached to petrified stems and leaves, from the impossibility of 
examining their internal structure and of finding the spores. 
External and variable forms exactly like small fungi are often 
mere unorganized bodies, produced by some mechanical or chem- 
ical action. All the remains of plants and even the shales over- 
lying the semi-anthracite coal of Trevorton, Penn., are covere 
with small round vesicles, of different sizes, looking exactly like 
erie, and are filled with a brown powder resembling spores. 
Sometimes the coal itself is full of them. They have probably 
been formed by the ebullition of the whole matter accidentally 
stopped during a strong gaseous emission. le 
Another very remarkable fungus, Polyporites Bowmannt, 18 
described by Lindley and Hutton in the fossil flora of Great 
Britain, (vol. i, No. 65). This species, or at least one, agreeng 
exactly with the figure and description of the English authors, 
was found in black bituminous shales overlying No. 1B coal at 
Johnstown, Penn. It is an hemispherical or reniform boey; 
marked with concentrical zones, especially distinct near and 
* Proceedings of the Geological Society of London, (Dec. 14, 1859). 
