450 



PROCEEDINGS OF THE ACADEMY OF 



[June, 



If we combine the conclusion from Table I with Table II we see 

 that snails in the exposed positions tend to be dark as well as those 

 in the sheltered places, while those in the bay shore tend to be the 

 lighter colored. 



The following table includes the results of collections made at 

 stations separated by no barrier, near together, but on a substratum 

 of different colored rocks. The numerous black basalt dykes that 

 everywhere cut the red granite make a number of collections of this 

 sort possible. Only a very few of the possible ones have been studied. 



In general, more light-colored snails are found on the red rocks 

 than on the black rocks. The association of yellow forms with the 

 environment is inconclusive. There does not seem to be any correla- 

 tion from these few cases. Thirty-three collections from red rocks 

 average 4% yellow. Fifteen collections from black rocks average 

 4.7% yellow. 



In this region there are occasional outcrops of a banded rock, a 

 chlorite schist. That there might be a correlation between striped 

 forms and schist is a possibility that may be investigated. The 

 collections from the red granite given in the table are those made 

 nearest to the chlorite schist. This comparison was not in mind 

 when the collections were made, so the stations are often several 

 miles apart. 



