90 BOOK OF SPECIES. 
a great tubercle ; mouth small, sub-rotund, white; 
columella yellow. 34. 
M. rriqvETER. Oblong, sub-fusiform, sub- 
triangular in its transverse outline, somewhat 
plaited longitudinally, and transversely furrowed ; 
white, sometimes with rufous splotches; varices 
membranaceous ; lip crenated; aperture elliptical. 
W. 25. 16. 
*** Tail short ; more than three varices. 
M. saxartinis. Sub-fusiform, very ventri- 
cose, with six foliated varices, which are usually 
