J. W. Dawson— Paleozoic Land Snails. 409 
and is between Coal 87 and Coal 88 of Logan’s section, being 
about 42 feet below Coal 87. The next horizon, and that in 
which the shell was first discovered, is 1217 feet of vertical - 
thickness higher, in group XV of Division 4 of my section. 
The shells occur here in erect Sigillarie, standing on Coal 15 
of Logan’s section. The third horizon is in group XXVI of 
Division 4, about 800 feet higher than the last. Here also the 
shells occurred in an erect Stgillaria. 
In the lowest of these three horizons, the shells are found, 
as already stated, in a thin bed of concretionary clay of dark 
gray color, though associated with reddish beds. It contains 
oneles priscus as well, though this is very rare, and there are 
a few valves of Cythere and shells of Nazadites as well as carbon- 
aceous fragments, fronds of ferns, Zrzgonocarpa, ete. The Pupe 
are mostly adult, but many very young shells also occur, as well 
as fragments of broken shells. he 
or in a carbonaceous mass composed mainly of vegetable debris. 
Except when crushed or flattened, the shells in these reposito- 
ries are usually filled with brownish calcite. From this I infer 
that most of them were alive when imbedded, or at least that 
they contained the bodies of the animals; and it is not improba- 
ble that they sheltered themselves in the hollow trees, as is the 
habit of many similar animals in modern forests. Their resi- 
dence in these trees as well as the characters of their embry- 
ology are illustrated by the occurrence of their mature ova. 
hey may also have formed part of the food of the reptilian 
animals whose remains occur with them. In illustration of this 
T have elsewhere stated that I have found as many as eleven 
unbroken shells of Physa heterostropha in the stomach of a 
modern Menobranchus. I think it certain, however, that bot 
the shells and the reptiles occurring in these trees must have 
been strictly terrestrial in their habits, as they could not have 
found admission to the erect trees unless the ground had been 
sufficiently dry to allow several feet of the imbedded hollow 
trunks to be free from water. In the highest of the three 
horizons the shells occurred in an erect tree, but without any 
other fossils, and they had apparently been washed in along 
with a grayish mud.* 
* The discovery of the shells in this tree was made by Albert I. Hill, 0.E. 
