'^^ A MANUAL OF AMERlo'AN LAND SHELLS. 



Of foot conspicuously furrowed. In motion the shell lies perfectly flat 

 on the extreme posterior portion of the body, the eye pednncles stand- 

 ing nearly perpendicularly, and the head with tentacles thrust out some 

 way beyond the base of eye-peduncles; eyes scarcely visible; animal 

 vei y short posteriorly. 



This peculiar shell is distinguished by its discoidal form, greenish 

 color, the line revolving lines upon its whorls, and the singular teeth 

 which are placed in the interior of the outer whorl. These teeth are ar- 

 ranged in pairs, on the external side of the parietes of the cavity, one 

 of each pair being on the superior and one on the inferior part of the 

 whorl. They are prominent, white, and conical, and may be discovered 

 though the semi-transparent shell. One pair is so near the aperture 

 as easily to be seen on looking into it ; the other is distant nearly one- 

 half a volution from the peristome, and is of course invisible except 

 through the shell. At least one pair will be found to exist in every 

 specimen when carefully sought for. In one instance I noticed a third 

 pair still further within the whorl. 



i^oticed under the bark or in the interstices of wet and decaying 

 wood, and under layers of wet leaves and stones in damp places in 

 forests. 



Vallonia, Risso. 



Animal heliciform (see Bost. Journ. I^at. Hist., I, Plate IX, Fig. 2); " 

 other characters as in Patida. 



Shell umbilicated, depressed, diaphanous; whorls 3^-4; aperture 

 oblique, subcircular; peristome white, thickened, reflected, its margins 

 contiguous or converging. 



The single known species is circumpolar, common to the three conti- 

 nents. In North America its range is shown below; in Europe it is 

 found everywhere, reaching indeed Northern Africa, the Azores, Madeira, 

 &c.; in Asia it occurs in Siberia, Thibet. This wide distribution, so 

 unusual in the land shells, suggests great antiquity for the species. It 

 is said to have been found in the Red and Norwich Crag (see Prestwich, 

 Quart. Journ. Geol. Soc, XXVII, 493). 



Jaw low, wide, slightly arcuate, ends but little attenuated, blunt; 

 ^"-38. cutting margin Mithout median projection; an- 



y^^^nmmMj)^ ^''''''''' ^''''^''''^ ^^'^^ numerous crowded, broad 

 <SA>^ ^A^ ribs, denticulating the lower margin (Fio-. 27 



Jaw of r. pulchella. (Morse.) X M V^ *= ' 



I 



