GENERA OF SHELLS. 65 



PUPA. Shell cylindrical, generally thick ; 

 aperture irregular, semi-oval, rounded and 

 subangular inferiorly ; margins nearly equal, 

 reflected outwards,- disjoined above ; a colu- 

 mellar lamina, firmly fixed, being interposed. 



P. mumia, uva, sulcata, Candida, labrosa, fusus, tridentata, 

 fasciolata, zebra, unicarinata, rnaculosa, clavulata, ovularis, 

 germanica, cinerea, tridens, quadridens, polyodon, variabilis, 

 frumentum, secale, avena, granum, fragilis, dolium, umbili- 

 cata, muscorum, armifera, corticaria, rupicola, contracta, 

 exigua, fallax, ovata, pentodon. 



CLAUSILIA. Shell generally fusiform, slen- 

 der, somewhat obtuse at summit; aperture 

 irregular, rounded oval ; margins united, free, 

 reflected outwards. 



The essential character of the clausilia is, that the 

 two borders of the aperture are completely united, free 

 in their contour, and reflected outwards. 



C. torticollis, trimcatula, retusa, costulata, corrugata, in- 

 flata, teres, denticulata, collaris, papillaris, plicatula, rugosa. 



BTJLIMUS. Shell ovate, oblong or turreted ; 

 aperture entire, longitudinal; margins very 

 unequal, disunited above ; columella straight, 

 smooth, entire at the base, not channelled. 



The last whorl of the spine of the bulimus is larger 

 than the penultimate ; the shell is never orbicular, like 

 the helix ; it differs from the pupa by the great ine- 

 quality of the two margins of the aperture, the right of 

 which is sometimes considerably thickened. 

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