58 CLASS GASTEROPODA. 
One species, celebrated for the high price it commands, the 
Turbo Scalaris, L., Chemn., LV. clii. 1426, &c.—vulgo, Sca- 
lata,—is distinguished by the whorls only coming in contact 
at the point where the ribs unite them, the intervals being 
open. 
A second species, the Turbo clathrus, Linn., List. 588, 50, 
51, is not marked by this peculiarity : it is more slender, and 
is commonly found in the Mediterranean. 
Some terrestrial or fresh-water subgenera, in which the 
aperture is entire, round, or nearly so, and operculated, may 
be placed here. Of this number is the 
CycLostoma, Lam. 
The cyclostoma should be distinguished from all the others 
because they are terrestrial, as, instead of gills, the animal has 
merely a vascular net-work spread over the parietes of its 
pectoral cavity. In every other respect, however, it resem- 
bles the other animals of this family : the respiratory aperture 
opens in the same way above the head by a great solution of 
continuity ; the sexes are separated ; the penis of the male is 
large, fleshy, and reflected into the pectoral cavity ; the two 
tentacula are terminated by blunt tubercles, and two other 
tubercles placed on their external base support the eyes. 
The shell isa spiral oval, with complete whorls, trans- 
versely and finely striated ; and its aperture in the adult is 
surrounded witha small ridge. Itis closed by a small round 
operculum. Found in woods, under moss, stones, &c. 
The most common is the Turbo elegans, List. 27, 25, about 
six lines in length, and of a greyish colour; found under all 
the mosses. Add Turbo lincina, List., &c. 
VALVATA, Miill. 
The valvata inhabit fresh water; their shell is convoluted 
in almost one plane, like that of a planorbis, but the aperture 
