_ 1886.) Zs Littorina litorea Introduced or 1 ndigenous ? 937 
was found along with such species as Purpura lapillus, Natica 
heros, Buccinum undatum, Nassa obsoleta, Nassa trivittata, etc., 
but he makes no mention of ZL. litorea. Mr. G. F. Matthew, in 
his account! of investigations into an undisturbed shell-heap on 
the shore of Passamaquoddy bay, New Brunswick, after men- 
tioning the occurrence of several littoral species, says: “ The 
tock periwinkle (Littorina rudis) is occasionally found * * * 
but the common European periwinkle (Littorina Litorea), now so 
common on this coast, is entirely wanting.” In a private letter 
to the writer the same gentleman says: “I have seen no trace of 
L. litorea in any shell-heap.” That the Indians would have col- 
lected the smaller native periwinkle and other small littoral spe- 
cies, and not the larger English one, were the latter present, is in- 
conceivable, no matter whether the former had been collected for 
food or only accidentally introduced into the shell-heaps. The 
same causes should have introduced Z. /itorea if it had existed at 
these places. Again the conclusion is forced upon us that if the 
shell existed in America at the time of the formation of the shell- 
“Heaps, it must have been confined to Nova Scotia. We have no 
Published lists of shells from the Nova Scotia shell-heaps, nor 
as the writer been able to find by private inquiry any satisfac- 
tory account of them. 
All of the facts that we have so far mentioned in connection 
With this shell show that if it existed at all in America previous 
0 the present century, it must have been confined to the coast of 
Nova Scotia, There are other general considerations which show 
tin all probability it did not exist there. One of these we 
have already mentioned—the fact that it was not introduced in 
same way as Z. palliata, by way of Greenland, and therefore 
Was probably not naturally introduced into America at all. . 
Many undoubtedly European species of both animals and 
Plant could be named which, upon their artificial or accidental 
troduction into this country, have driven out and well-nigh 
exterminated closely-allied native species. Everywhere upon the 
__ “ast of Nova Scotia as well as that of the rest of Acadia and New 
land, Z. ditorea is doing precisely this, driving out the native 
-~ palliata, Everywhere the native form gives way before it and 
_ mes rare, just in proportion as the English form becomes 
abundant, This fact of itself gives us strong a priori grounds 
* Bull, N. B. Nat, Hist, Soc., IIT, 1884, 
