158 A. EF. Verrill— The Bermuda Islands; Geology. 
Parr IV.—II. PaLeontTo.toey. 
24. Fossils of the Walsingham Formation. 
In a former chapter (pp. 68-74), I have discussed the occurrence 
of numerous fossil land-shells, nine of which are now extinct, in this 
formation. Besides the land shells we find in it the well-known 
large West Indian “whelk” (Livona pica, fig. 60). The latter is 
often abundant, just as it is in the later zolian limestones. It was 
undoubtedly carried up from the sea beaches to the sand hills by 
the land hermit crab ( Cenobita diogenes, fig. 60), which is still found 
on the modern sand hills with the ancient fossil shells on its back, 
for these fossil shells are so commonly weathered out entire that 
they are always available. Many of these ancient specimens still 
retain the external color and the pearly luster of the interior nacreous 
lining. This species, though still common in the West Indies, seems 
to have died out in Bermuda in modern times. There is no authentic 
record of recent living specimens.* 
a. Land Shells. 
The most interesting of the fossil shells belong to a genus of 
snails peculiar to Bermuda, named Pecilozonites by Pilsbry. It 
differs anatomically from all the related genera, but its nearest allies 
are found in eastern North America. It is by no means certain that 
all the extinct species referred to this genus really belong to it, but 
most of them strongly resemble the living forms. At the time when 
this formation was deposited the genus had already reached its 
maximum development and greatest differentiation, for at that 
remote time the largest known species (P. Welsoni) was very abun- 
dant, while at the same time the smallest and most diversely formed 
species, such as P. cupula and P. Dailli, were in existence. Six 
species and five well marked varieties are now recognized. All the 
species and all but one of the varieties are found fossil in this forma- 
tion. This proves that the genus had been established or had orig- 
inated here at a period long anterior to the deposition of the oldest 
rocks now known on the islands, for such differentiation implies a 
very long period of evolution. Three species of the genus and four 
varieties are now extinct. The other associated species belong to 
well known American and West Indian genera. 
* See ‘‘ The Bermuda Islands,” p. 296; these Trans., xi, p. 708, for a discus- 
sion of this matter. 
