354 E. M. KINDLE 
have never seen this shell in the shallow water of the river, although 
other shells are common there. It appears, therefore, that it lives 
Fic. 8.—River bottom clay and silt shoved on bank of an island by ice scour, 
Mackenzie River. © 
abundantly in the deeper parts of the river and reaches the local- 
ities where found on the banks as a result of ice excavation and the 
vagaries of strong current action and transportation during the 
Fic. 9.—A clay island protected from erosion by a bowlder pavement 
spring break-up. When the ice breaks on the river in the spring, 
ice jams occur which raise the river to abnormal heights at various 
localities. McConnell' has given the following striking descrip- 
1 Geol. Surv. of Canada, Ann. Rept., IV, 1888-89 (1890), p. 87 D. 
