WEST COAST PULMONATA. 15 



No. 7) as 31esomphlx durantl ccelata, as I consider it merely 

 a sub-species, or perhaps only a variety of that species, 

 differing chiefly in a thicker and coarser shell, caused by 

 more abundant lime and moisture in the localities it in- 

 habits on the mainland, than on the islands where the type 

 was discovered. Mr. Binne}^ agrees in this opinion. 



Succinea a vara Say. 



Mr. Binney (2d SuppL, p. 46), reports tliis eastern species 

 also from California, but the locality is not given. It oc- 

 curs in some regions east of the Sierra Nevada, but is not 

 known yet on their west slope. 



Pupa arizonensis Gabb. (P. Vertigo) Ovata Say. 



These two species, referred to in Bull. 7, page 361, are 

 also additions, the former only found on the east slope of 

 the Sierra; the latter, a common eastern species, apparently 

 straggling west to near San Diego. 



E. — Xew Notes on Native Species. 



Limacoids. 



Referring now to the table of species given in Bull. 7. p. 

 367, I may further explain the reasons for grouping them, as 

 there done, in difterent order from that adopted by the 

 latest classifiers, Avho have so thoroughly investigated the 

 internal anatomy of these animals. 



Their external characters, besides being those most easily 

 recognized, are also those by which they are brought under 

 the etfects of surrounding influences, and thus they become 

 naturally grouped into series, of which the members ex- 

 hibit similar relations to the laws of nature, independent to 

 a great extent of their internal structure. 



Although not claiming that this similarity in habits and 

 appearance constitutes a basis for scientific grouping quite 

 independent of their organization, it becomes necessary to 

 use it in giving their history. 



