24 ZONITIDA. 
cONULUS, Fitz., 1833. (Trochiscus, Held,1837. Petasia, Beck, 
1837.) Shell small, pellucid, corneous, globosely turbinated, or 
conic, thin, perforate or imperforate; aperture lunar, oblique; 
peristome simple. Universal, including several American and 
European species. Z. fulvus, Drap. (xciii, 98). 
coNULOopOLITA, Bottger. No umbilicus as in Conulus. 4. 
Raddii, Bottger. Caucasus. 
GAsTRODONTA, Albers, 1850. Shell subperforate or umbilicated, 
orbicularly depressed, light horn-color, sometimes glassy, with 
more or less numerous wrinkle-like striz ; whorls 5-7; aperture 
lunate, its base generally furnished with fold-like denticles not 
reaching its margin; peristome simple, acute. United States. 
Z. interna, Say (xciii, 100°. 
VENTRIDENS, Binney and Bland, 1869. Shell small, subper- 
forated or umbilicated, orbicular, convex ; aperture lunar, with 
revolving pliciform teeth within the base; peristome simple, 
sharp. Z. gularis, Say. Z. suppressa, Say. United States. 
oODONTOSAGDA, Albers, 1860. Shell umbilicated, depressed, 
thin, white; whorls six, the last with convex base; aperture 
somewhat oblique, lunar, with three double lamellze within; 
peristome acute, the columellar margin slightly reflexed. Z. 
polyodon, Weinland and Martens. Hayti. 
PROSERPINULA, Albers, 1860. Shell scarcely perforated, dis- 
coidal, hyaline, transparent; whorls 44, planulate, the last slightly 
impressed at the base, with a shining callus around the perfora- 
tion, spiral laminze reaching the margin; peristome acute. 4. 
discoidea, Ads. 2sp. Jamaica. 
HELICODIscUS, Morse. Minute, planorboid, with revolving 
strive, aperture lamellarly toothed within the outer lip. Z. line- 
atus, Say (xciii, 9,10). United States. 
micropHysa, Albers, 1860. (Microconus, Strebel and Pfeffer.) 
Shell umbilicated, depressed, thin, striulate, scarcely shining ; 
spire flattened with distinct suture; whorls 4-5, slightly convex, 
slowly increasing, the last not deflected ; aperture rounded-lunate ; 
peristome thin, the margin converging. Z. Boothianus, Pfr. 
(xciv, 15). 37 sp. West Indies. 
PELLA, Albers, 1860. Shell umbilicate or imperforate, orbic- 
ular depressed, thin, striate or striately plicate; whorls five, 
slightly convex; aperture lunately rounded; peristome simple, 
acute; columellar lip dilated, reflected, free. 4. bisculpta, Ben- 
son (xciv, 16). So. Africa. 
SAGDINELLA, Morch, 1872. Not characterized. H. Didrich- 
senit, Moreh. Nicobar Is. 
STRIATURA, Morse, 1864. Central plate of the radula enormous ; 
buccal lamina almost smooth, with a median furrow and notch. 
Z. milium, Morse. United States. 
JANULUS, Lowe, 1852. Shell umbilicated, depressed orbicular, 
