PETTERD : ON SOME NEW TASMANIAN HELICES. 217 



A pure white species allied to H. Roblini mihi, but that 

 species is finely striated throughout and its umbilicus is not 

 nearly so open. To H. Bassi Brazier, it is so closely related 

 that it may possibly be but a variety, but it is much smaller, 

 has a much less shallow umbilicus and the riblets are coarser 

 than in its larger congener, x^ll three are of the same habits, 

 found on the under surface of boulders, generally in rather 

 dry situations, and all are of extreme rarity. 



14. H. Barrenensis, n. sp. 



Shell small, discoid, thin, regularly,- somewhat closely 

 ribbed ; under the lens the interstices strongly decussate ; 

 embryonal whorl smooth, horny brown; spire much sub- 

 merged gradually; whorls 5-|-, last rounded, base with ribs as 

 above, umbilicus widely open, shallow, freely exposing the 

 ■ whorls; aperture vertical, semilunar, faintly flattened above; 

 peristome simple. 



Diam., greatest 2, least i^; height i mil. 



Habitat — Furneaux Group, Bass Straits. (Mr. R, M. 

 Johnston). 



Invariably in clusters, gregarious in shallow depressions 

 on the sand hillocks. Closely allied to H. lirata Cox, from 

 New South Wales. 



Hobart Town, Tasmania, 



December 14th, i8y8. 



