diate in facies between that of the Coasl Range and Arizona 

 Systems of the California Province, and the Baja California 

 System of tin* .Mexican Province, but contains a number of 

 peculiar species, particularly helicies, while Micrarionta, the 



group of maritime Epiphragmophoras is almost wholly re- 

 stricted within its limits. 



PART I— LAND MOLLUSCA. 



Henry M. Edson and Harold Hannibal. 



Factors of Distribution. 



The distribution of the Los Angeles System land Mollusca, 

 as with land mollusks in general, is strictly in accordance with 

 the life-zones recognized by botanists, mammalogists, and 

 ornithologists. Abrams* admits four such zones in this portion 

 of California, the Canadian, Arid Transition, Upper Sonoran, 

 and Lower Sonoran. 



FAUNAS OF THE LIFE ZONES. 



The Canadian Zone, belt of the Lodge-pole Pine, Limber 

 Pine, Glaucous Willow, and Quaking Aspen, includes the high 

 mountain cienagas and the upper slopes of the highest peaks. 

 Landshells in this zone are by no means rare, but consist 

 wholly of minute widespread forms. 



The following occurf : 



fEuconulus fulvus :;: ?Vertigo occidentalis 



Punctum californicum fVitrina alaskana 



Pyramidula cronkhitei Zonitoides arboreus 



f?Succinea stretchiana Zonitoides pugetensis 



fThysanophora ingorsolli 



In the Arid Transition zone, belt of the Yellow l'ine, 

 Sugar Pine, and White Fir. embracing the forested areas of 

 the higher mountains, terrestrial mollusks are infrequent in 

 southern California, due not improbably to the unfavorable 

 ^■round-cover afforded by the pines, which form the predom- 

 inate portion of the flora. 



The following species are known or may be looked for in 

 the forest belt: 



?Amalia hewstoni Pyramidula cronkhitei 



Ariolimax columbianus ?Succinea streetiana 



Punctum californicum Zonitoides arboreus 

 Punctum conspectum Zonitoides pugetensis 



*Abrams, LeBoy; A Phytogeographic and Taxonomic Study of the 

 bouthcru California Trees and Shrubs, L910, \>. 307 ff. 



t.\i! asterisk preceding a speeies indicates that it is confined to the 

 zone in which it occurs and is restricted to the Los Angeles System, a 

 dagger that it is characteristic of the /.one in which it is found, two 

 daggers that it is introduced. A question mark denotes that further 

 study is necessary to settle the zonal distribution. 



in 



