194 HELIX. 
3-toothed ; one of the three on the pillar lip, 
other two on the outer white lip. Breadth about 
half an inch. 
alternata, (striped snail,) shell somewhat convex, 
striped with alternating rays of a light and 
dark colour; whorls five, crossed by equi-dis- 
tant raised lines ; lip curved, with a pearly hue 
within; umbilicuslarge. Breadth about three- 
fourths of an Inch. 
glaphyra, (shining snail,) shell much depressed, 
smooth, pellucid, thin, fragile ; whorls five, 
rounded, obsolete irregular cross wrinkles ; 
whitish beneath ; umbilicus middling. Breadth 
about half an inch. 
Section B. FLat-orsep Hexix, or Pianorsis 
of Bruguieres. Spire depressed or sunk, so as 
not to be raised above the central plain of the 
whole coil. 
érivolvis, (short-tail snail,) shell sinestral (coiling 
from leit to right, beginning at the tip of the 
spire, when the back of the animal is upwards,) 
pale yellow, brownish chesnut; somewhat keel- 
ed above and beneath, particularly in the young 
state, whorls three or four, with raised, equi- 
distant, fine cross lines 5 spire concave ; aper- 
ture large, bluish-white within; umbilicus large. 
Largest breadth about half an inch. Sometimes 
itis a little larger, very dark coloured, with a 
reddish mouth within. 
bicarinatus, shell sinistral, pale yellow or brown- 
ish, somewhat keeled above and translucent be- 
neath ; spire retuse-umbilicate, forming a cavi- 
ty as deep as that of the base ; aperture large, 
