488 Shells of Massachusetts, 
cuna 2, Cingula 2, Turritella 2, Pyramis 1, Odosto- 
mia 5, Cerithium 5, Pleurotoma 3, Cancellaria 1, 
Fusus 10, Pyrula 2, Ranella,1, Rostellaria 1, 'T'richo- 
tropis 1, Purpura 1, Buccinum 9, Columbella 1, Spi- 
rula 1. : 
At least seventy of our marine species are also 
found on the transatlantic shores, and a few terres- 
trial species are also found on both continents. Of 
these last may be mentioned Heliz aspersa, hortensis, 
cellaria, pulchella, perhaps lucida, and Bulimus 
lubricus. 'There are several other shells which, if 
not the same, are very closely allied ; such as Suc- 
cinea, and some of the species of Limnea and Plan- 
orbis. Mr. Forbes, in his Report to the British As- 
sociation, in 1839, puts down Limnea ‘palustris and 
stagnalis, as American species, alluding probably to 
our L. appressa and L. elodes. I will not pretend to 
dispute this, because their similarity is great, and it 
would be very difficult to prove them either identical 
or distinct. It appears to me that they present dif- 
ferences which are at once perceived, if they cannot 
be plainly described, so that any one might readily 
separate them from each other. i 
It is not difficult to account for the transportation 
and subsequent propagation of the terrestrial species 
from one continent or island to another. This I5 
well known to be the case in England, and Mr. 
Forbes, in the report above referred to, gives numer- 
ous examples of it, and in- some instances gives Us 
the historical period and manner of the transfer. 
This, we know, is the history of Helis asper 
hortensis, and cellaria in this country,— shells w. 
