HELICID^. 39 



Discula^ Lowe, 1854. Shell like Tectula, but depressed. H. 

 polymorpha, Lowe, 20 sp. Madeira. 



Gallina, Lowe, 1854. H. rotula^ Lowe. Porto Sancto. 



PLECTOTROPis, Albers, 1860. (Tliea, Albers, 1850.) Shell 

 openly and profoundly umbilicate ; lenticular, thin, diaphanous, 

 carinate ; whorls six-and-a-half, slowlj- increasing, the last not 

 descending; carina acute, compressed, crenulate ; aperture 

 securiform or subrhomboidal ; upper margin of peristome thin, 

 somewhat expanded, basal margin scarcel}^ dilated, shortly 

 reflected. 38 sp. Eastern Asia, Australia. H. elegantissima^ 

 Pfr. (xcv, 51). 



VALLONiA, Risso, 1826. (Circinaria, Beck, 1837. Lucena, 

 Moquin-Tandon, 1855. Corneola, Held, 1837. Chilostoma, 

 Fitz., 1833. Glaphyra, Albers, 1850. Amplexus, Brown, 1827. 

 Zurama, Leach, 1820.) Shell somewhat depressed, diaphanous, 

 umbilicated ; whorls three or four, rounded ; aperture oblique, 

 subcircular ; peristome with white reflected lip, its extremities 

 joined by a parietal callus. Species all minute. IT. pulchella, 

 Miiller (xciv, 41, 42), inhabits the northern regions of both 

 hemispheres, and is a common shell throughout the northern 

 United States and British America ; unlike the essentially 

 American forms it seems to prefer open gardens to damp wood- 

 lands, thus betraying its European origin. H. pulchella, Miill. 



4 sp. Europe, United States, Australia. 



PETASiA, Beck, 1837. (Trochiscus, Held, 1837. Perforatella, 

 Schliiter, 1838. Dibothrion, Pfr., 1855.) Shell thin, narrowly 

 perforated, turbinately globose, closely wound ; whorls 6-8, the 

 last not deflected ; aperture obliquely lunate ; peristome labiate 

 within, patulous or subreflected, basal margin dentate. H. bidens, 

 Chemn. (xciv, 43). 2 sp. Europe, Siberia. 



FRUTicicoLA, Held, 1837. (Helicella, Stabile, 1864.) Shell 

 umbilicate or perforate, depressly globose, sometimes hairy ; 

 whorls 5-6, somewhat convex; aperture widely lunar or lunately 

 rounded ; peristome acute, slightly expanded, labiate within, 

 basal margin reflected. H. fruticum, Mlill. 



Monacha, Hartmann, 1840. Shell conical, perforate ; peristome 

 labiate and reflected. H. mcarnata, Miill. 



Nummulina^ Kobelt, 1871. H. nummus^ Ehrenberg (xciv, 45). 



5 sp. S3a'ia, etc. 



Garthusiana, Kobelt, 1871. (Teba, Strobel, 1850. Theba, 

 Stabile, 1864.) H. car thusiana, Mnll. European, 



Zenobia, Gray, 1821. Shell conoidal, perfoi'ate, peristome 

 simple. H. cinctella, Drap. European. 



Trichia, Hartmann, 1840. (Petasina, Morch, 1852.) Shell 

 depressed, closely whorled, usually pilose; columellar margin 

 callous. H. villosa^ Drap. Mostly European. 



CAM^NA, Albers, 1850. Umbilicated, sinistral, turbinated 



