ODOSTOMIA. 293 



dual from which the earher known Warrenii was de- 

 scribed. For in this last the spiral lines upon the base are 

 comparatively obscure, and the subscalar structure of the 

 volutions whose lower portions in this variety, in lieu of 

 being perpendicular, are somewhat more ventricose, is less 

 apparent, being, as it were, convexly bevelled off. 



The shell is slender, tapering to a moderately fine point, 

 thin, transparent, lustrous, and of an unifoi-m white or 

 sallow white tint. To the eye it seems smooth or nearly 

 so, but on careful examination displays numerous and regu- 

 larly impressed spiral lines on the basal half of the body 

 whorl, besides irregularly diffused and very indistinct, 

 longitudinal wrinkles of increase. An oblique and very 

 distinct, yet not canaliculated, suture deeply divides the 

 five rounded turns of the spire from each other. The 

 whorls are of rapid longitudinal increase (hence the penult 

 is decidedly high), and are more or less subscalar from the 

 suddenness of their superior projection : the apical nucleus 

 is less prominently and obliquely disposed than usual, and 

 sinks into the summit of the shell. The body is almost 

 equal to the spire in length ; its periphery is not at all 

 angulated ; its basal declination is gradual, convex, and 

 somewhat produced. The mouth, which occupies from 

 about two-fifths to three-sevenths of the entire length, is 

 narrow and oblong-ovate ; it is suddenly contracted above 

 by the swollen base of the preceding whorl, and is some- 

 what effuse, and not very broadly rounded at the base. 

 The outer lip, which is simple acute, and disposed to curl 

 inwards rather than expand, is at first but moderately 

 convex. The much receding pillar lip is devoid of any 

 fold ; it occupies nearly three-fourths of the total length of 

 the aperture, and is very slightly curved, and not reflected. 

 There is a small but distinct umbilicus. A single line was 



