GASTEROPODA. Th 
She muute, cylindrical, truncated; whorls striated trans- 
versely; aperture oval, entire; peristome continuous; operculum 
sub-spiral ! 
Animal with short, diverging triangular tentacles; eyes 
centrally behind; head bi-lobed; foot short, rounded at each 
end. (Forbes.) 
The truncatellcee are found on stones and sea-weeds between 
tide-marks, and survive many weeks out of the water. (Lowe.) 
They walk by contracting the space between their lips and foot, 
like the geometric caterpillars. (Gray.) They are found semi- 
fossil along with the human skeletons in the modern limestone 
of Guadaloupe. 
Distribution, 15 species. West Indies, Britain, Mediterranean, 
Rio, Cape, Mauritius, Philippines, Australia, Pacific. (Cuming.) 
? LiTHOGLYPHUS, Megerle. 
Type, L. fuscus (Pl. [X., Fig. 22). 
Shell naticoid, often eroded; whorls few, smooth; aperture 
large, entire; peristome continuous, outer line sharp, inner lip 
callous; umbilicus rimate; epidermis oliyaceous; operculum 
pauci-spiral. 
Distribution, 5 species. Europe and Oregon. 
FAMILY VII.—PALUDINIDA. 
Shell conical or globular, witha thick, olive-green epidermis ; 
aperture rounded; peristome continuous, entire; operculum 
horny or shelly, normally concentric. 
Ammal with a broad muzzle; tentacles long and slender ; 
eyes on short pedicels, outside the tentacles. Inhabiting fresh 
waters in all parts of the world. 
PALUDINA, Lam. Rivyer-snail. 
Etymology, palus (paludis), a marsh. 
Synonym, Viviparus, Gray. 
Type, P. Listeri (Pl. [X., Fig. 26). (P. vivipara, Fig., 68.) 
Shell turbinated, with round whorls; aperture shightly angular 
behind; peristome continuous, entire; operculum horny, con- 
centric. Animal with a long muzzle, and very short eye- 
pedicels ; neck with a small lappet on the left side, and a larger 
on the right, folded to form a respiratory siphon; gill comb-like, 
single; tongue short; teeth single, oval, slightly hooked and 
denticulated; uncini 3, oblong, denticulated. The paludine are 
