1916.] NATURAL SCIENCES OF PHILADELPHIA. 449 



subject to the smoothest water has the darkest. This difference is 

 very striking and the intermediate stations show intermediate ratios. 



This has led the writer to classify the shores according to the wa\ 

 These are arbitrary divisions and of course every intergradation is 

 found, but in most cases there is very little hesitation how a given 

 -i ation should be described. If a great uncertainty exists, the station 

 was placed in both classes. 



Sea cliff or surf exposed to the open sea. An ordinary row boat 

 can practically never land with safety. 



Bay exposed to a moderate surf during high winds. Except at 

 those times a small boat can easily land on the shore without danger 

 of accident. 



Harbor so smooth that a row boat can practically always make a 

 landing. 



In the tables which follow the stations nearest together are always 



compared. 



Table I. 



Condi- Station No. of 



Locality. tion. No. Individuals. Lt. White. 



Bakers Id Surf. 23 65 6.1 



Bay. 24 167 20.7 6 



Seal Harbor Surf. 54 176 2.8 



Bay. 56 34 55.6 44 



Cranberry Id Surf. 10 319 30 4.3 



• Surf. 11 195 59 9.7 

 Bay. 13 204 15 5.7 



• We can conclude that in general the snails on the most exposed 

 situations are darker than those found in the bay. 



Table II. 



Condi- Station Xo. of % 



Locality. tion. No. Individuals. Lt. White. 



G — ngsId | a j bo , 3? lit S 1 2 1! 



BuckelId gSo, iS Hi % % 



Bear Id Bay. 43 277 24 12| 



Harbor. 44 6< 10§ H 



Oronold Bay. 19 55 11 7 



Harbor. 18 184 50 2, 



Southwest Harbor. Bay. 37 194 29| 19 



Harbor. 36 196 I" I 



Harbor. 35 273 25£ 11 



Harbor. 47 172 14$ 6J 



