OF NORTH AMERICA. 63 



universally distributed over the greater part of North America north 

 of the 38 of north latitude. These are shown in the subjoined table : 



stagnalis appressa distributed throughout ten regions. 



caperata distributed throughout eight regions. 



obrussa distributed throughout eleven regions. 



galbana distributed throughout seven regions. 



palustris distributed throughout eleven regions. 



Three species are universally distributed between the 30 and 50 

 of north latitude. 



parva distributed throughout seven regions. 



humilis modicella distributed throughout nine regions. 



obrussa distributed throughout nine regions. 



A number of species are peculiar to certain regions to which they 

 are at present restricted. These are shown in the following tables : 



CENTRAL AMERICAN REGION. 

 attenuata. columella championi. 



WEST INDIAN REGION. 

 francisca. cubcnsis aspirans. 



CAROLINIAN REGION. 

 humilis. neopalustris. 



'. CALIFORNIAN REGION. 



bulimoides. sonomaensis. gabbi. 



COLUMBIAN REGION. 



occidentalis. hinkleyi. jacksonensis. 



^ apicina solida. montana. 



COLORADOAN REGION. 



hendersoni. 



GREAT BASIN REGION. 



utahensis. pilsbryi. 



UPPER MISSISSIPPIAN REGION. 



palustris blatchleyi. danielsi. reflexa hemphillianu. 



CANADIAN REGION. 



stagnalis perampla. pallida. catascopium adamsi. 



cyclostoma. davisi. catascopium niagarensis. 



owascoensis. nasoni. emarginata ontariensis. 



petoskeyensis. woodruffi. contracta. 



palustris alpenensis. pilsbryana. 



NOVA SCOTIAN REGION. 

 elodes shurtleffi. pscudopinguis. decollata. 



YUKONIAN REGION. 

 perpolita. alaskensis. petersi. 



ALASKAN REGION. 



atkaensis. truncatula. 



GREENLANDIAN REGION. 



holbollii. 



