200 BOYSIDIA. 



only a single one), an interpalatal, and one to three supra- 

 palatals, which do not show in the figures. All of these plicae 

 are hooked, except when very small. 



Some variation may be noted in specimens from Landour, 

 the type locality. The summit is more obtuse in some ex- 

 amples (fig. 1), smaller in others (figs. 2, 4), these having a 

 fraction of a whorl more, fully 5 whorls. The Japanese speci- 

 mens have 5 to 5% whorls. The smallest specimen measured 

 is a trifle under 2.1 mm. long. Two topotypes received from 

 Benson measure : 



Length 2.4, greatest diam. 1.75 mm.; 4% whorls (fig. 1). 



Length 2.45, greatest diam. 1.9 mm.; 5 whorls (figs. 2, 4). 



The number of minor plicae varies somewhat in different 

 individuals. I have seen specimens with as many as 16 

 lamellae and plicae. 



"The animal has four tentacula, the superior pair bearing 

 the percipient points or eyes, the inferior very short. The 

 foot is hyaline, the tentacula and neck fuscous. The shell is 

 carried horizontally. It is very local, although tolerably abun- 

 dant where found. It creeps among moss, on damp rocks, 

 generally in places which are seldom or never visited by the 

 sun, in some of the lofty and precipitous glens of the moun- 

 tains near Landour. It seems to be a capricious species. On 

 a rock on which I found it abundantly one year, I could not 

 obtain a specimen at the same season in the following year" 

 (Benson) . 



Col. Godwin-Austen (1872) thought that Hydrocena milium 

 Bens, might be the young of this species, but could not reach 

 a positive conclusion. He states that the specimens of plici- 

 dens from Mussoorie are of smaller size. He alludes also to 

 an undescribed Pupa like plicidens from the Jhelum Valley, 

 Kashmir, collected by Theobald (Proc. Malac. Soc. Lond., iii, 

 262). 



The writer has been criticized for forming a section (Ben- 

 sonella) for this species. If the shell were larger, so that its 

 peculiar characters could be seen readily, it would hardly 

 have been associated in one section with the true Boysidias. 

 No naturalist who has treated of B. plicidens seems to have 



