530 Annals of the Carnegie Museum. 



a second outlet, that through the Ottawa river, closed. If new 

 islands have been formed since, their island career has no relation to 

 glacial history. They were formed simply through the agency of 

 erosion. 



We hope at some future date to pay a more leisurely visit to these 

 islands and make a more thorough study of the geology and botany 

 with the idea of getting additional light on their age, as this may 

 indicate how long it takes a species, such as Pyramidida solitaria — 

 which goes back to inter- if not pre-glacial time unchanged from its 

 present typical form — to change to distinct, and strongly marked 

 races, as on the islands. 



For purposes of record, the findings at the different islands are here 

 set down: 



West Sister Island, Ohio. 



Polygra albolabris (Say) Helicodiscus parallelus (Say) 



profunda strontiana Clapp. Punclum pygmaeum (Draper) 



zaleta (Binney) Bifidaria armifera (Say) 

 elevata (Say) contracta (Say) 



inflecla (Say) holzingeri Sterki. 



monodon fralerna (Say) tappaniana (Adams) 



Vitrea indentata (Say) peniodon (Say) 



Zonitoides arboreus (Say) Vertigo milium Giddings 



minusculus (BinnejO Vallonia pulchella (Miiller) 

 Pyramidula solitaria (Say) parvula Sterki. 



alternata eriensis Clapp. Carychitim exigiiuni Say. 

 cronkhiiei anthonyi Pilsbry 



Green Island, Ohio (Formerly Strontian Island). 



Polygyra profunda strontiana Clapp 

 zaleta (Binney) 

 inflecta (Say) 

 Pyramidula solitaria strontiana Clapp. 



alternata eriensis Clapp. 

 Succinea avara Say. 



Middle Island, Ontario. 



Polygyra profunda (Say) Zonitoides arboreus (Say) 



zaleta (Binney) minusculus (Binney) 



palliata (Say) Circinaria concava (Say) 



fraiidulenta Pilsbry Bijidaria armifera (Say) 

 inflecta (Say) contracta (Say) 



monodon fralerna (Say) corticaria (Say) 



Pyramidula solitaria Say Vallonia parvula Sterki. 

 solitaria roseo-apicata Clapp. Succinea avara Say. 

 alternata (Say) 



