50 HELICID A. 
cerAstus, Albers, 1860. Shell rimate, ovate, costulate or 
striulate, thin, corneous ; whorls 6-7, somewhat convex, the last 
as long as the spire; aperture rounded-ovate; peristome 
reflected, with approaching margins joined by a thin callus. 
B. distans, Pfr: 3 sp. India, E. Afmica: 
HAPALUS, Albers, 1850. (Harpalus, Austin, 1872.) Shell 
imperforate, elongated, very thin, transparent; whorls six or 
seven, the last more than half the total tenes columella 
callous, twisted above; aperture oval, angular above ; peristome 
simple, sharp; outer lip arcuated above. B. Grateloupi, Pfr. 
17 sp. India, East Indies, Philippines, Guinea, ete. 
RAPHIELLUS, Pfeiffer, 1855. B. achatinellinus, Forbes. Gala- 
pagos, 
Bouuimuuus, Leach, 1814. 
Syn.—Peristoma, Kryn., 1833. Zebrina, Held, 1837. 
Distr.—545 sp. Tropical America. 
Shell oblong, aperture longitudinal, edentulate, peristome thin, 
margins unequal; columella integral. Jaw arcuate, closely 
plicate. Lingual membrane (of B. dealbatus) broad, central 
teeth tricuspid, the median cusp very long; laterals bicuspid ; 
the dentition varies in the different groups. 
The following sections form the subgenus :— 
GONIOGNATHMUS, Crosse and Fischer, “1875. It is characterized 
by a jaw having plications that are angulated in the centre, and 
by lingual teeth with narrow inner cuspidation, nearly as long 
as the median eusp, which is obtuse and broad. 
Eudioptus, Albers, 1860. Shell imperforate, ovate or ovate- 
oblong, smooth, shining, pellucid, thin; whorls 5-6, the last 
exceeding the spire; aperture ovate or ovate-oblong ; columella 
strict, thin; peristome acute, simple. C. pseudosuccinea, Moric. 
6 sp. South America. 
Plectostylus, Beck, 1837. Shell imperforate, thin, translucent, 
conic-oval; spire acute; columella intrant, slim; peristome 
thin, sharp. 3B. Chilensis, Lesson (xeviii, 27). 18 sp. South 
America. 
Drymeus, Albers, 1850. (Hamadryas, Albers, 1850.) Shell 
perforated or umbilicated, oblong, lightly striate or rugose ; 
spire elongated, sharp ; whorls seven or eight; aperture oblong- 
oval; columella subtortuous; peristome simple; columellar lip 
reflected. B. xanthostomus, VOrb. (xeviii, 28). 100 sp. Mexico, 
Central and South America, West Indies. 
Leiostracus, Albers, 1850. Shell thin, perforated, oblong- 
conic, shining; spire elevated, apex acute; whorls seven or 
eight; aperture oval or oblong -oval ; peristome thin, more or 
less expanded ; columellar lip dilated, reflected. B. Mericanus, 
Lam. (xcvii, 20). 38 sp. Florida, West Indies, Mexico, So. 
America, 
