418 PROCEEDINGS OF THE ACADEMY OF [July, 



clausilium is also longer, and the whole plate is strongly twisted 

 spirally. 



Section HEMIPH^EDUSA Bttg. 

 Group of C. ptyehochila. 



In this group the right lip or interlaraellar space is more or less 

 crenate; the superior and subcolumellar lamellae are marginal, the 

 inferior lamella somewhat receding, thickened below, strongly sig- 

 moid within, and in the middle of the dorsal aspect it is low, wide 

 and bifid, as if composed of two cords twisted round one another. 

 The lower palatal plica is very strong, elevated in the middle where 

 the lunella joins it, the latter being very strong below, weak above. 

 The clausilium (PI. XXIII, figs. 26-29) is wider in the middle 

 than in Hemiphcedusa, tapering above and below, strongly curved 

 toward the thickened, obtuse apex, and with the lateral margins 

 bent nearly at right angles with the rest of the plate, forming a 

 sort of spout-like distal extremity (PL XXIII, figs. 27, 28). 



This group is probably entitled to separate sectional rank. It is 

 related to the Japanese group of C. platydera, but differs in the 

 form of the inferior lamella within the last whorl, and in the 

 clausilium. 



Key to species. 



1. Inferior lamella thickened but simple below: 



a. Surface strongly ribbed; subcolumellar lamella somewhat 

 dilated in the part adjacent to the lower palatal plica, 



C. Bernardii. 

 a'. Surface more finely costulate : 



b. Lunella becoming very weak and curving inward 



above, strong and high below; subcolumellar 



lamella not dilated near the lower palatal plica; 



upper palatal plica weak, . . C. crenilabium. 



I'. Lunella straight; shell more obese, C. ptychochila. 



2. Inferior lamella bifid below, C. excellens. 



Clausilia Bernardii Pfr. PI. XXIII, figs. 30, 31, 32. 



C. Bernardii Pfr., Journ. de Conchyl., IX, 1861, p. 267, PI. 15, figs. 1, 

 2 ; Monogr. Hel. Viv., VI, p. 426. 



This species was described as from Siarn. It has not been found 

 by any later collectors in that region, and there are grave reasons 

 for considering the locality erroneous. 



The original specimens from Bernardi's collection were dis- 



