172 HYPSELOSTOMA-BOYSIDIA GROUP. 



West Australia: East Wallaby Island, Houtmans Abrolhos 

 (Walker). 



Pupa waUaby en-sis E. A. SMITH, Proc. Malac. Soc. London, 

 i, 1894, p. 97. 



' ' The teeth of this species are very characteristic, and block 

 up the aperture to a considerable extent. The three parietal 

 are much smaller than the rest, and situated close together, 

 the central one being the largest. That on the columella is 

 large, lamelliform, and prominent. The central palatal tooth 

 is narrow, long, and extends inwards ; those on each side of it 

 are shorter, but a trifle more prominent, perhaps. 



"~P. macdonnelli Brazier, from Fitzroy Island, N. E. Aus- 

 tralia, is a little shorter than this species and has more feeble 

 armature in the aperture" (Smith). 



Mr. B. B. Woodward, who has kindly examined the type 

 specimen for me, states that the columellar lamella ascends 

 within. The species is therefore related to the polymorphic 

 G. larapinta. It differs by the unusually small aperture (only 

 one-fourth the total length, while in larapinta it is at least 

 one-third), and the narrower contour of the shell. It has not 

 been figured. 



THE HYPSELOSTOMA-BOYSIDIA GROUP. 



These forms are similar to Gastrocopta in dentition and in 

 the thin shell of not many whorls (4 to 6). They differ from 

 Gastrocopta by the markedly conic spire, when the shell is 

 Pupiform. In certain aberrant forms the spire is much de- 

 pressed, and in all the last whorl becomes horizontal or (usu- 

 ally) ascends. Its tendency is to become tangential. The 

 peristome is generally continuous. They inhabit a large part 

 of the Oriental Region. 



Gredler and von Mollendorff have discussed the connection 

 of Hypselostoma and Boysidia through several species of in- 

 termediate form. The latter authority, however, would not 

 unite both in one genus, holding that the free and produced 

 last whorl of Hypselostoma sufficiently differentiates it from 

 Boysidia. 



It may be assumed that the primitive forms of the Hypse- 



