GASTEROPODA. 257 



She m'nute, cylindrical, tnincatGd ; 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 truncatellce 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. 



JDistrihution, 15 species. "West Indies, Britain, Mediterranean, 

 Eio, Cape, Mauritius, Philippines, Australia, Pacific. (Cuming.) 



? LiTHOGLYPHTJS, Megcrle. 



Tijjie, L. fuscus (PI. IX., Fig. 22). 



Shell naticoid, often eroded ; whorls few, smooth ; aperture 

 large, entire ; peristome continuous, outer line sharp, inner lip 

 callous ; umbilicus rimate ; epidermis oKvaceous ; operculum 

 pauci-spii-al. 



Distribution, 5 species. Europe and Oregon. 



Family YII. — PALTjDmiD^. 



Shell conical or globular, with a thick, olive-green epidermis ; 

 aperture rounded ; peristome continuous, entire ; operculum 

 horny or shelly, normally concentric. 



Animal with a broad muzzle ; tentacles long and slender ; 

 eyes on short pedicels, outside the tentacles. Inhabiting fresh 

 waters in all parts of the world. 



Paludin'A, Lam. Eiver-snail. 



Etymology, palus {paludis), a marsh. 



Synonym, Viviparus, Gray. 



Tijpe, P. Listeri (PI. IX., Fig. 26). (P. vivipara, Fig. 68.) 



Sliell turbinated, with round whorls ; aperture slightly 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 paludinse are 



