HELIX. 259 



rounded, not exhibiting any of the volutions ; base con- 

 vex, indented around the^umbilicus. Two or more rows 

 of very minute, white teeth, radiating from the umbilicus, 

 are seen through the shell, within the base of the last 

 whorl. 



Greatest transverse diameter one-eighth of an inch. 



GEOGRAPHICAL DISTRIBUTION. Noticed hitherto only 

 in Vermont among the Green Mountains, and in the 

 adjoining parts of New York. 



REMARKS. This species possesses characters so 

 marked that it, at first, is not likely to be mistaken 

 for any other. The numerous narrow whorls visible on 

 its upper and plane surface, while only one is seen 

 below, together with its minute, round umbilicus, and 

 narrow aperture, would sufficiently distinguish it ; but 

 there is another character still more peculiar. There 

 are from two to four rows of very minute, delicate, white 

 teeth, on the lower side of the interior of the last whorl, 

 radiating from the centre. One row is usually so near 

 the aperture as to be seen within it with the aid of a 

 microscope ; the others are more or less remote : each row 

 contains from five to six distinct teeth. They are visible 

 through the shell. The transparency of the shell is so 

 great that frequently the sutures of the upper surface 

 can be seen through it, when viewed on the base. With 

 the living animal within, the shell has a roseate tinge. 

 This beautiful little species has usually been considered 

 to be very distinct in its characters ; but recent observa- 



