173 



muscorum, and as such Adams' species is now recognized, 

 though I have already pointed out some slight differences 

 in the two shells. Since Adams' discovery of the species, 

 in this country, it has been found on certain islands in 

 the Gulf of St. Lawrence, as well as in New York State. 

 In the year 1862, Mr. Charles B. Fuller found it in 

 Maine, near Portland. In some localities near that city, 

 known to have been examined by early collectors without 

 meeting with it, it has been collected by thousands. At 

 Oak island, Chelsea, a famous collecting ground of Dr. 

 Gould, Dr. Binney and others, no evidence of the ex- 

 istence of this species there is recorded. In the year 

 1860, Prof. W. C. Cleveland found it in the greatest 

 abundance. In this case it can be positively asserted that 

 the species has been introduced within twenty years. 

 The collectors of Salem and Lynn had failed to observe its 

 occurrence in Essex County. Last summer I discovered 

 the species in great abundance on Lowell island in Salem 

 harbor. From these evidences it is quite certain that this 

 minute land shell is being distributed with considerable 

 rapidity. 



It will be found that, as in the case of plants, the land 

 species of mollusks are being widely distributed through 

 railway traffic. I have often found, at Portland, minute 

 land shells clinging to firewood that had been brought 

 from the interior of the state. 



The remarkable rapidity in the diffusion of Littorina 

 litorea is of special interest in this connection. This 

 well-known European species was first observed on this 

 continent by Mr. Willis, of Halifax, N. S., many years 

 ago. Since that time, it has been rapidly and widely dif- 

 fused along the coast of New England. 



In 1870, Mr. Fuller found a few specimens in Portland 

 harbor, and about the same time at Kennebunk in Maine. 



