HELICIDA. 39 
Discula, Lowe, 1854. Shell like Tectula, but depressed. #H. 
polymorpha, Lowe. 20sp. Madeira. 
Callina, Lowe, 1854. H. rotula, Lowe. Porto Sancto. 
PLECTOTROPIS, Albers, 1860. (Thea, Albers, 1850.) Shell 
openly and profoundly umbilicate ; lenticular, thin, diaphanous, 
carinate; whorls six-and-a-half, slowly increasing, the last not 
descending; carina acute, compressed, crenulate; aperture 
securiform or subrhomboidal; upper margin of peristome thin, 
somewhat expanded, basal margin scarcely dilated, shortly 
reflected. 38 sp. Eastern Asia, Australia. H. elegantissima, 
Pien(xev,;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, H. pulchella, 
Muller (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, Mull. 
4 sp. Europe, United States, Australia. 
PETASIA, Beck, 1837. (Trochiscus, Held, 1837. Perforatella, 
Schluter, 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). 2sp. 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, Miill. 
Monacha, Hartmann, 1840. Shell conical, perforate ; peristome 
labiate and reflected. H. incarnata, Mull. 
Nummulina, Kobelt, 1871. H.nummus, Ehrenberg (xciv, 45). 
5 sp. Syria, ete. 
Carthusiana, Kobelt, 1871. (Teba, Strobel, 1850. Theba, 
Stabile, 1864.) HH. carthusiana, Mull. European. 
Zenobia, Gray, 1821. Shell conoidal, perforate, 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. 
CAMANA, Albers, 1850. Umbilicated, sinistral, turbinated 
