192 BOYSIDIA. 



Genus BOYSIDIA Ancey. 



The shell is conic, narrowly umbilicate or perforate, open- 

 ing out broadly in the last half-whorl, which is straightened 

 and built forward to the ventral face; composed of 5 to 6y 2 

 convex whorls; the surface minutely granular. Aperture 

 subvertical, essentially hexodont, but additional teeth may be 

 present, or the basal fold may be wanting ; angular and pari- 

 etal lamellae independent or concrescent into a sinuous lamella. 

 Peristome expanded, either continuous or interrupted and ad- 

 nate above. 



Type: B. dorsata (Anc.). 



Distribution : from the Yangtze Valley to Java. 



For the present, two groups which will possibly be con- 

 sidered of generic value are included in this genus: (1) BOY- 

 SIDIA proper, and (2) BENSONELLA with the subgenus Para- 

 boysidia. 



Key to Species of Boysidia, Bensonella and Paraboysidia. 

 a. Columellar lamella obliquely descending inward. 



b. Angular and parietal lamellae united into one lobed 

 or sinuous lamella. 



c. Alt. 3.3 to 4, diam. about 2.5 mm. 



B. hunana, no. 1 ; B. dorsata, no. 2. 

 c 1 . Alt. 2.75, diam. 2 mm.; angulo-parietal la- 

 mella widest in the middle. 



B. hangchowensis, no. 3. 

 & 1 . Angular and parietal lamellae separate, parallel. 



B. strophostoma, no. 4. 



a 1 . Entering portion of the columellar lamella horizontal, not 

 descending inwardly. 



b. Lamellae and plicae terminating outwardly in hooks; 

 angular and parietal lamellae separate and parallel. 



B. plicidens, no. 5. 

 b 1 . Ends of the lamellae and plicae not hooked. 



c. Peristome thick, white, not continuous across 

 the parietal wall. 



d. Angular and parietal lamellae concres- 

 cent into one lamella with a spur on the 

 right side; length 5 mm. 



B. robusta, no. 6. 



