THE CHICAGO ACADEMY OF SCIENCES. 



Of the above regions, the Canadian has produced the largest 

 number of species (14). The Greenlandian region has but one peculiar 

 species, and the West Indian, Carolinian and Alaskan regions have but 

 two species peculiar to their areas. 



A study of the distribution maps reveals certain interesting facts 

 regarding the present dispersal of North American Lymnaeas. The 

 largest number of species is found between the 38th and the 60th 

 degrees of north latitude. North and south of these parallels the 

 number of species notably decrease. 



TABLE SHOWING DISTRIBUTION IN LATITUDE. 



Species and varieties north of 60 13 



Species and varieties between 38 and 60 85 



Species and varieties south of 38 29 



Species and varieties south of 30 7 



Species and varieties south of 20 3 



It will be noted in the above table that the number of species first 

 increases and then decreases, the number steadily falling until but three 

 species are represented south of 20. This table also indicates the 

 northern distribution of the family, 85 species and varieties, or 85 per 

 cent being found between 38 and 60 of north latitude. It is note- 

 worthy that but three species of Lymngeas have been recorded from 

 the tropical zone. 



SPECIES AND VARIETIES NORTH OF 60. 



stagnalis apprcssa. 

 stagnalis ivasatchensis. 

 truncatula. 

 perpolita. 



jholbollii. 



obrussa. 



palustris. 



vahlii. 



vahlii pingelli. 



SPECIES AND VARIETIES BETWEEN 38 



stagnalis appressa. 



stagnalis perampla. 



stagnalis lilliance. 



stagnalis wasatchcnsis. 



sanct&maria. 



occidentalis. 



lepida. 



columella. 



columella chalybea. 



columella casta. 



utahensis. 



megasoma. 



haldemani. 



truncatula. 



d odd si. 



bulimoides. 



bulimoides cockcrelli. 



humilis rustica. 



ferruginea. 



obrussa. 



obrussa peninsula. 



obrussa exigua. 



obrussa decampi 



galbana. 



petoskeyensis. 



palustris. 



palustris alpenensis. 



palustris blatchleyi. 



palustris desidiosa. 



neopalustris. 



elodes. 



elodes jolietensis. 



elodes shurtleffi. 



reflexa. 



vahlii arctica. 

 randolphi. 

 alaskensis. 

 peter si. 



AND 60. 



traskii. 



vahlii. 



vahlii arctica. 



pa Hi da. 



catascopium. 



catascopium adamsi. 



catascopium niagarensis. 



davisi. 



nasoni. 



woodrufK. 



pseudopinguis. 



decollata. 



sumassi. 



jacksonensis. 



gabbi. 



e marginal a. 



emarginata mighelsi. 



