HELIX. 95 



SECTION II. LIP SIMPLE. 



Comprising all those species, the margin of the aper- 

 ture of whose shell is not in any degree reflected, al- 

 though it is sometimes a little thickened. The apertnn\ 

 properly speaking, is never furnished with teeth, but in 

 some of the species there are lamellar processes or 

 prominent teeth within the aperture. 



In the species belonging to this section, the terminat- 

 ing axis of the shell, about which the whorls revolve, 

 being never covered with testaceous matter, the umbili- 

 cus may be said to be always open ; but it varies from 

 a mere perforate point at the centre of the base of the 

 shell, to an expanded cup-like cavity, exhibiting the infe- 

 rior surface of all the volutions. The degree of separa- 

 tion differs considerably in the same species. 



c. Aperture destitute of teeth or folds, within. 



H. alternata, arborea, cellaria, chersina, cumberlandiana, demissa, egena, 

 electrina, fuliginosa, indentata, inornata, intertexta, ligera, liinatula, lucida, 

 lucubrata, miuuscula, ottonis, rotula, selcnina, solitaria, sportella, striatellu. 

 strigosa, subplana. 



f. Aperture having one or more teeth or folds, within. 



H. gularis, iaterna, lasnaodon, lineata, multidentata, perspectiva, sup- 

 pressa. 



