60 ACHATINIDA. 
striate or costulate; aperture oval, short, about one-third or 
one-fourth the length of the shell; columella arcuate, abruptly 
truncate; peristome simple, acute. A. eyanostoma, Ruppell. 
PERIDERIS, Shuttleworth, 1856. (Corona, Albers [pt. |, 1850.) 
Shell imperforate, ovately conical or oblong, apex papillary, 
shining, striate, decussated by very minute spiral lines, epidermis 
very thin; whorls 6—7, the last usually obsoletely angulated ; 
suture wrinkled, marginate; aperture short, suboval, columella 
slightly twisted, obliquely subtruncate ; peristome simple, acute. 
A, balteata, Gould (xevili, 41). 18sp. West Africa. 
LIMICOLARIA, Schum., 1817. Shell perforate, conically or 
turreted oblong, last whorl shorter than the spire; aperture 
oblong, suboval; columella vertical, protracted at the base; 
peristome simple, thin, straight, columellar margin dilated, arcu- 
ately reflexed. L. Aiquatoria, Rve. (xeviii, 42). 31 sp. Africa. 
PSEUDACHATINA, Albers, 1850. Shell solid, oval, turriculated ; 
whorls eight or nine, the last obtusely angular at the periphery, 
and exceeding half the length of the shell; columella subtortu- 
ous, a little arcuated, truncate-tuberculate below; aperture oval ; 
peristome thick, slightly reflected; lips united by a callosity. 
P. Downesti, Gray (xeviii, 44). Tsp. W. Africa. 
coLUMNA, Perry, 1811. Shellalways sinistral, much elongated, 
decussated, whorls oblique; constricted at suture ; apex obtuse; 
columella callous, spirally twisted, truncate at base; peristome 
simple, sharp. OC. flammea, Martyn (xevili, 46). 4 sp. W. 
Africa. Fossil Achatine occurring in the eocene of Upper 
Missouri, and in the Paris basin, are referred to this group. 
CHILONOPSIS, Fischer de Waldheim, 1848. Shell bulimiform, 
thick; aperture ear-shaped, both lips greatly thickened, the 
eolumellar lip tuberculate above, obliquely truncate below. 
Bulimus auris-vulpina, Chemn., which occurs subfossil in the 
island of St. Helena, is the type of this group. 
StrenoayrA, Shuttleworth, 1850. 
Syn.—Sira, Schmidt, 1855. Subulina, Adams, 1855. 
Distr.—250 sp. World-wide, tropical and temperate regions. 
Shell elongated, turriculated, whorls numerous, apex obtuse 
or truncate; aperture oval, small, columella thin, straight ; 
peristome simple, sharp. 
Median tooth of the radula very small; jaw thin, feebly 
arcuated, vertically plicate. 
oBELiscus, Beck, 1837 (— Stenogyra, restricted). Shell long, 
imperforate, elongate-turreted, scarcely shining; whorls 10-18, 
last about one-fourth the total length; columella straight, not 
truncate; peristome simple. SS. obeliscus, Moric. (xcix, 31). 
38 sp. West Indies, Central and South America, Natal, Philip- 
pines, etc. 
