BOYSIDIA. 201 



seen the hooks of the teeth, and part of the teeth which appear 

 to be constant have not been noticed at all. My conclusions 

 are based upon considerable series from India, China and 

 Japan, including topotypes from Benson. 



Though long known from India, B. plicidens was first turned 

 up in China and Japan by Mr. Hirase 's collectors. It may be 

 wanting in a large part of central and southern China ; I can- 

 not otherwise understand how it escaped such observant nat- 

 uralists as Pere Heude, Dr. von Mollendorff, Mr. Schmacker, 

 and others. At present its range appears to be strikingly dis- 

 continuous. 



Subgenus PARABOYSIDIA Pilsbry. 



Paraboysidia PILS., this vol., p. 174, July 18, 1917. 



The shell has the shape and minutely granulose surface of 

 Boysidia, but differs by having the angular and parietal 

 lamellae separate, long and parallel (except in B. robusta and 

 B. kelantanensis, where they are connected or concrescent). 

 The columellar lamella enters horizontally (the inner end not 

 turned downward as it is in Boysidia) ; plicee situated as 

 usual. Peristome is either continuous or interrupted above, 

 expanded and thickened, a nodule on the inner margin limit- 

 ing the sinulus. 



Type B. paviei B. & D. 



Distribution : India to Tonkin, south to Java. 



This group is closely related to Bensonella and to Gyliau- 

 chen, and indeed it may be regarded as the parent stock from 

 which these groups were derived. Some of the species have 

 the teeth minutely spiniferous, as in Gyliauchen. 



B. robusta is an accelerated form in which the angular and 

 parietal lamellae have become concrescent. I do not think it 

 directly related to the Chinese Boysidias, but rather a conver- 

 gent form belonging to a collateral phyletic line. 



6. BOYSIDIA ROBUSTA Bavay et Dautzenberg. PL 35, figs. 1, 2. 



Shell large for the genus, rather solid and turbinate. Spire 

 conoid. Whorls 6, rather convex, joined by an impressed 

 suture, the first whorls smooth, the rest ornamented with 



