( 66 )  (Pectinibranchi. Trochoida.) 
f. Cyclostoma, Lam. 
A vascular net-work 2 Tentacula terminated Eyes on two tubercles 
on the partitions of the by blunt tubercles. near the base of the ten- 
pectoral cavity, instead tacula. 
of branchiz ; respira- 
tory cavity communi- 
cating with the exte- 
rior air by a lateral! 
cleft, 
g- Helicina, Lam. (1) y 
Head _proboscidi- 2 Filiform tentacula, Eyes at the outer base. 
form, bilabiate ; respi- 
ratory cavily as in Cy- 
clostoma. 
hk, Valvata, Muller, (2) 
With branchiz. 2 Slim tentacula. 
Eyes at the superior 
base, 
é. Paludina, Lam. (3) 
With branchie; a 2 Pointed tentacula. Eyes at the outer base. 
very short trunk. PI. 
14 feel eRl. 17, fig. 
Fresh-water and Terrestral. 
J» Monodonta, Lam. 
Animal more orna- 
namented, generally 
with three filaments 
on each side as long 
as the tentacula. 
2. Trocuus. Lin. 
Mouth of the shellan- Three filaments at 
gular, more or less quad- each edge of the man- 
rangular, oblique to the tle, or appendages to 
axis. the foot. Pl. 17, fig. 3, 
4,.12*, 13. 
a. Trochus. 
6. Solarium. 
(1) M. Blainville is convinced that this is the place of the Helicina; but M. de 
Ferussac says that it has a collar, with the respiratory hole pierced to the left. 
(2) In the V. cristata the branchie, formed like a feather, proceed from under- 
neath the mantle, and float beyond it with a vibratory motion when the animal 
wishes to breathe ; on the right side of the body is a filament resembling a third 
tentaculum. 
(3) The female of the P. vivipara produces living young, which are found in her 
oviductus, in the spring, in all the stages of developement. Spallanzani asserts that 
these young separated at the moment of their birth, and nourished apart, repro- 
duce without fecundation like those of the Vine-fretter. The P. cristata one of 
the small species found in salt water ponds, and described by M. Beudant, moves 
its tentacula incessantly as oars when it sails on the surface of the water. 
