THE SNAILS OF GREENLAND 
21 
ninety-one in Iceland.* * * § Of the more hardy spiders the per¬ 
centage of survival is very different, for there are fifty-three 
species in Greenland and only twenty-four in Iceland.f 
The theory of the survival of species in Greenland may 
be tested by some other examples. Besides Helix hor- 
tensis about a dozen other kinds of land and fresh¬ 
water mollusks inhabit the country.J Eight of these either 
have their centre of distribution in Greenland or are 
quite peculiar to the country. These are Planorbis nathorsti, 
P. arcticus, Limnaea vahli, L. holbolli, Succinea groen- 
landica, Vitrina angelicae, Conulus fabricii and Pupa hoppii. 
The two species of Planorbis are also known from Labrador; 
Succinea groenlandica occurs in Iceland; P. arcticus has 
been met with in Scandinavia, Finland and Siberia. The 
first of the Limnaeas ranges from Greenland to Alaska, 
the other is peculiar to Greenland. The latter, however, 
is replaced in boreal North America by the closely-allied 
Limnaea retusa. Vitrina angelicae is not found in America, 
but occurs in Iceland and Norway. Conulus fabricii is pro¬ 
bably only a variety of the common Conulus fulvus of northern 
Europe, Asia and America, while Pupa hoppii is confined to 
Greenland. With the single exception of Planorbis arcticus 
all these species live at present well within the glaciated area, 
that is to say, within that portion of the northern regions 
supposed to have been either wholly or partially buried by 
ice during the Glacial Epoch. As none but Planorbis arcticus 
have ever been found fossil outside that area, we may assume 
with some justification that most of them originated in Green¬ 
land, and that all, at any rate, survived the Ice Age in that 
country. Planorbis arcticus, as Mr. Ivennard § informs me, 
has been taken in Pleistocene deposits in Denmark and in 
the south of England. (Compare also Kennard and Wood¬ 
ward’s paper.) 
It is more difficult to demonstrate that butterflies and moths 
* Poppius, B., “ Coleopteren des Arktischen Gebietes,” p. 428. 
t Strand, E., “ Arktische Araneae,” p. 436. 
\ Morch, O. A. L., “ Land and Fi’esbwater Mollusca of Greenland.” 
§ Kennard, A. S., and B. B. Woodward, “ Extinct post-pliocene 
Mollusca of Southern England,” p. 5. 
