108 LAND AND FEESH-WATER MOLLUSKS. 
without opacity; upper surface smooth or slightly 
wrinkled; whorls three and a half to four, rather 
flattened above; body whorl much larger than 
that preceding it; sutures well defined, deep 
and narrow; umbilicus moderately large; aper¬ 
ture oblique, crescent-shaped, broader than high ; 
diameter one-tenth to one-sixth of an inch. 
Helicella crystallina — (the Crystalline Snail) 
(PL VII., fig. 58)—is common among moss, 
herbagp, decaying leaves, and under stones in 
woods, pastures, and hedgerows. 
The shell is flattened, with the spire very 
slightly raised; colour white, or with a slight 
greenish tinge, very shining and transparent; 
under surface without opacity; upper surface 
smooth or slightly wrinkled; whorls four and a 
half to five, of gradual increase, the body whorl 
being but little larger than that preceding it; 
whorls flattened above; sutures well defined; 
umbilicus very small; aperture not very oblique, 
crescent-shaped, about as broad as high; dia¬ 
meter from one-twelfth to one-eighth of an 
inch. 
Helicella excavata — (the Excavated Snail) 
(PI. VII., fig. 52).—The shell is depressed, sub- 
globular; colour that of darkish horn, shining 
and transparent; under surface not obscured by 
any white opacity; upper surface strongly and 
regularly striated, the striae being continued 
