OF THE UNITED STATES. 135 



none; aperture somewhat angulated; labrum dilated, 

 reflected, pure white, at base adpressed to the body 

 whirl, abruptly narrowed on the inner edge beneath 

 the middle, and continuing thus narrowed to the su- 

 perior termination, leaving a projecting angle behind 

 the middle; labium with a large, robust, very ob- 

 lique, sub-arquated, pure white tooth. 



Greatest breadth, 7-8 of an inch. Column, 9-16. 



Found rather common in the vicinity of Cincinnati, 

 Ohio, it seems to be distantly related to thyroidus, 

 by the tooth on the labium, but this tooth is much 

 more robust; it differs more essentially by the much 

 more elevated spire, and by the superior half of the 

 dilated lip being abruptly narrowed so as to form a 

 prominent angle near the middle. It is also a much 

 thicker shell. 



tt Umbilicus closed ; labrum simple, 



8. H. *interna. Shell yellowish red; volutions 

 six or eight ; whoiis with regular, equidistant, ele- 

 vated, obtuse lines across them separated by regular 

 grooves; lines obsolete beneath; spire convex, little 

 elevated; aperture very strait, transverse less than 

 one half of the longitudinal diameter; labrum not re- 

 flected; within, upon the side of the labrum, two pro- 

 minent lamelliform teeth, of which the superior one 

 is largest, and neither of them attain the edge of 

 the lip; region of the base of the columella much in- 

 dented; umbilicus obsolete or wanting. 



