42 BOOK OF SPECIES. 
five, obliquely striated; aperture semi-circular ; 
diam.) B. .'T. 95. 
P. carinatTus. MHorn-colour, transparent, 
striated, nearly flat on both sides, with a promi- 
nent obtuse keel in the middle; diam. 3. B. 
8/7. 
P. sprrorBis. Whitish, striolate, a little 
concave on both sides ; outer whorl with a sharp 
keel in the middle, pale horn-colour; four or five 
whorls ; aperture heart-shaped, acute at the top ; 
faa. SBS O28. 
P. contortus. Nearly flat above, deeply 
umbilicate beneath, horn-colour, but generally in- 
crusted; whorls five, remarkably compact and 
equal; aperture very narrow, lunate; diam... B. 
T.96. 
P. nisprpus. Concave on both sides, with 
finely raised, hispid, spiral strie; whorls five ; 
the first large and rounded, pale horn-colour ; 
aperture roundish oval, dilated, higher than wide, 
with the upper angle much produced. ¢. B. 
v.87. 
P. nit1ipus. Orbicular, flattened, keeled at 
the circumference, umbilicated beneath, diaphan- 
ous, shining, pale horn-colour ; whorls four ; aper- 
ture oval, inclining to triangular; diam. 3. B. 
PE; 89. 
P. impRricatus. Flat above, umbilicate be- 
