A MANUAL OF AMERICAN LAND SHELLS. 25 



istic of California.- It is prolific of species and also varieties to a de- 

 gree which has cansed some confusion in the synonymy. Glyptostoma 

 is also peculiar to California. 



From Lower California and Mexico the Pacific Region has been 

 shown to be equally distinct, wanting entirely the Holospira, Glamlina, 

 Bulimulusy and Zonites of those regions. 



Failing on the north, east dnd south, the west alone is left to us from 

 whence to trace the pulmonate fauna of the Pacific Kegion, and here 

 the secret of its origin lies buried under the Pacific Ocean. 



II. — The Central Province extends from Mexico to the British posses- 

 sions, between the Rocky Mountains on the east and the Sierra Nevada 

 and Cascade Mountains on the west. 



The following are the species peculiar to the province : 



Limax nwntanus. - Polygyrella polygijrella. 



Patula strigosa. Mesodon Mullani {=(levius). 



Rempliilli. Pupa Arizonensis. 



Idahoensis. hordeacea. 



Horni. corpulenta. 



Microphysa IngersolU. 



The second of these species is also found on the eastern sloj)e of the 

 Eocky Mountains, in Wyoming and Dakota, in company with P. solitaria. 

 I have shown above that the last-named species has penetrated the 

 Central Province, and even passed the barriers of the Pacific Province 

 at the Dalles. 



To the above must be added, as inhabiting the province, but not 

 peculiar to it, the following species from the Pacific Province, inhabit- 

 ing either slope of the Sierra ]S"evada : Vitrina Pfeifferi. Zonites Whit- 

 neyi, Succinea Sillimani, and Suecinea Stretchiana. The following also, 

 from the Oregoniau Region of the Pacific Province, Mesodon devius, 

 Arionta Toionsendiana, and Macrocyclis Vancouverensis, are found at its 

 most northern point, though the former two species are reduced in size. 

 We find also over the Central Province the following species, whose 

 derivation can readily be traced to the north : Zonites minusculus, fulvus, 

 and indentatus, Vallonia pulehella, Helicodiscus lineatus, Patula striatella^ 

 Ferussacia subcylindrica. (See above, p. 19.) 



Arionta Boicelli, a Lower California species, is omitted from the list, 

 its presence in Arizona being exceedingly doubtful.* 



* A specimen of Patula strigosa confounded with A. Bowelli gave rise to this mistake. 



