151 



This species resembles S. Redfieldianum ; but the shell 

 is larger, the spiral lines are smaller, and the spire is larger 

 in proportion at the last whorl. 



Stoastoma Petitianum. Shell between globose and dis- 

 coidal : dingy white : with'eight or [ten raised slender spiral 

 lines, of which three or four are visible on the spire, and as 

 many others which are more minute : spire moderately eleva- 

 ted, convex : whorls three and one-half, moderately convex, 

 with a lightly impressed suture ; last whorl well rounded : 

 aperture much contracted behind the labrum, which is but 

 moderately produced, and is double, with the outer margin 

 scarcely modified by the larger spiral lines ; labium moder- 

 ately detached from the penult whorl : umbilicus rather small, 

 with the spiral lamella but moderately developed. 



Mean divergence about 125° ; height .04 inch ; greatest 

 breadth .06 inch ; least breadth .05 inch. 



Stoastoma Anthonianum. This shell is like the preceding ; 

 but the spire is much depressed ; the spiral lines are rather 

 stronger ; and the aperture is very campanulate, the labrum 

 being very much produced before the deep constriction. 



Mean divergence about 145° ; height .035 inch ; greatest 

 breadth .07 inch ; least breadth .055 inch. 



