406 PROCEEDINGS OF THE ACADEMY OF [April, 
THE FOSSIL LAND SHELLS OF BERMUDA|! 
BY ADDISON GULICK. 
Last summer (1903), through advantages offered by the new Bio- 
logical Station in Bermuda, I was able to collect the shells on which 
this paper is based. In the study of the material I owe much to Dr. 
H. A. Pilsbry, of the Academy of Natural Sciences of Philadelphia. 
It will be necessary in the discussion of the fossils to compare them 
with the species that are now native, in the looser sense, to the islands. 
In drawing the line between these and the snails supposed to have 
been brought by commerce, I shall follow Dr. Pilsbry’s latest paper on 
the “Air-breathing Mollusks of the Bermudas.’ I shall also rule 
out all the littoral species, including T’rwncatella, because the fossil 
beds were not situated where such shells could be expected. 
The most unsatisfactory feature of work on Bermudian fossil land 
shells is the difficulty in determining the ages of the various deposits. 
The rock of Bermuda is exclusively solidified dunes of calcareous sand, 
and the soil is the rust-colored residue of the weathered rock. In 
weathering, the surface of the rock becomes completely broken up 
into pockets and crevices packed with the earth. It is estimated’ 
that every inch of earth must represent eight or nine feet of rock eroded, 
and thus when it is possible to judge of the average depth of soil formed 
over a deposit, that depth can be made an index of the age of the 
deposit. 
Probably the oldest good fossiliferous deposit that I examined is 
collecting locality No. 807 (see Map No. 3) of the Bermuda Biological 
Station, at a hard-stone quarry on the west side of Knapton Hill, 
about midway between Hotel Frascati and ‘“Devil’s Hole.” At this 
point a layer of eight or ten inches of red earth containing shells was 
covered by an ancient dune. The dune has become hard limestone, 
and its top has been eroded until now the red earth in its pockets must 
represent a layer averaging not less than six inches in thickness. The 
series of Pacilozonites that we took from this bed is very incomplete, 
and the fossils of all the genera are poorly preserved, but notwith- 
standing this we are able to recognize at least eleven species and sub- 

1 Contributions from the Bermuda Biological Station for Research, No. 2. 
2 Trans. Conn. Acad., Vol. X. 
3A.E. Verrill, Trans. Conn. Acad., Vol. XI, p. 490. 
