Corneocyclas pulchella I Jenys) O 



Lymnaea palustris ( M iiller) 



Lymnaea solida ( Lea ) 



Lymnaea solida cubensis ( Pfeiffer) < > 



Lymnaea truncatula ( Miiller I 



Planorbis trivolvis (Say) 



Segmentina parva ( Say ) ( ) 



Segmentina dilatata (Gould) 



Physa f ontinalis ( Linne ) ( ) 



Physa f ontinalis acuta (Draparnaud) 



Paludestrina protea (Gould ) 



Paludestrina longinqua (Gould) O 



Flumnicola fusca (Haldeman) L 



Valvata tricarinata (Say) — 



The fauna of the Colorado' System (basin of the Colorado 

 River above The Needles) has not been thoroughly explored 

 conehologieally hut contains fully sixteen species and sub- 

 species of which eleven may he enumerated among the fauna 

 of the Arizona System which adjoins it on the south. 



Baja California System. 



Corneocyclas pulchella (Jenys) OOO 



Lymnaea solida cubensis (Pfeiffer) 



Lymnaea truncatula (Miiller) L 



Planorbis trivolvis (Say) O ( ) 



Segmentina anitensis (J. G. Cooper) K 



Segmentina peninsularis (J. G. Cooper) ... K 



The fauna of the Baja California System (Baja California 

 Peninsula proper) is extremely impoverished due to the des- 

 ert-like nature of the country. But six species are known 

 from the region, of which four are common to the Los Angeles 

 and Arizona Systems to the northward. Of these Lymnaea 

 truncatula has been obtained only from the higher mountains 

 of the Peninsula. 



Sonora System. 



The fauna of the Sonora System (streams (lowing west 

 from the Mexican Table-land south to the vicinity of Mazatlan I 

 is practically unknown. The following occur or may be ex 

 pected in this region. 



Anodonta cygnea impura ( Say) • 



"Glabaris" glaucus (Valenciennes) 

 Corneocyclas pulchella (Jenys) 

 Lymnaea solida cubensis | Pfeiffer) 

 Lymnaea truncatula (Miiller) 

 Planorbis trivolvis (Say) 

 Segmentina liebmanni (Dunker) 

 Physa fontinalis acuta (Draparnaud) 



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