GEOGRAPHICAL DISTRIBUTION. 33 



The above list shows the Interior Region to be remarkable for the 

 development of the section of Zonites familiar by the European Z. oli- 

 vetorum {Mesomphix of Alb. ed. 2). Of the disintegrated genus Helix 

 the section or genus Mesodon is most developed. This is almost exclu- 

 sively a North American subgenus, as is also Triodopsis, which is also 

 greatly developed in the Interior Region. 



In addition to the species included in the above list as inhabiting all 

 of the Interior Region, there is a large group of species found within its 

 limits, but having a more restricted range. They are found in what 

 may be called the Cumberland Sub-Region. This is comprised in the 

 southern portion of the Appalachian chain, situated in Eastern Tennes- 

 see and the adjoining counties of North Carolina, with an offshoot into 

 the mountains of West Virginia. 1 



The following species are peculiar to this Sub-Region : 



Vitrina latissima. Stenotrema labrosum. 

 Zonites capnodes. Edgarianum. 



subplanus. Edvardsi. 



sculptilis. barbigerum. 



Elliotti. maxillatum. 



demissus. Triodopais Rugeli. 



capsella. introferens. 



placentula. Mesodon Clarki. 



lasmodon. Christyi. 



Patula Cumberlandiana. Lawi. 



teiiuistriata? Wheatleyi. 



Polygyra fastigans. Wetherbyi. 



Troostiana. Downieana. 



Hazard!. Pallifera Wetherbyi. 

 Stenotrema spinosum. 



Of these, several have spread beyond the limits given above for the 

 Sub-Region. Thus, Zonites lasmodon and Stenotrema, spinosum have been 

 found in Northern Alabama. Polygyra Hazardi has also spread into 

 Northern Alabama, and equally into Georgia and Kentucky. Steno- 

 trema labrosum and Edgarianum in Alabama, and in one case have been 

 collected in Arkansas. S. barbigerum, S. maxillatum, and Zonites cap- 

 nodes have found their way into Alabama and Georgia ; Mesodon Clarki 

 into Georgia. Zonites subplanus has been found even in Pennsylvania, 



protect itself from the moment of its birth, while, if deposited as an egg by the parent, it 

 might perish from drought. 



1 For a description of its physical and climatic characters, see Vol. I. 122. It is there 

 designated as the Southern Interior Section, and is given a wider western range. 



