1870.] On the Land Shells of Bourhon. 413 



29. Vertigo (al^ja) Borbonica, H. Ad., Zool. Soc. Proe. 1868, 

 p. 290. 



Very local, also found on huge masses of stone, at a great 

 elevation. 



30. Vertigo (Pagodella) incerta, n. sp. 



Shell very closely resembling Vertigo {Pagodella) ventricosa, H. 

 A d., from Mauritius ; there are, however, two parietal teeth and 

 within the outer lip a distinct, well-developed tooth, with occasion- 

 ally another small, indistinct one close to it ; the columellar is 

 slightly more dilated and sub-angulated ; rare, in company with 

 V.pupula near Salazie. 



This most perplexing of shells can only be distinguished from 

 JPagodella ventricosa, H. A d., Proc. Zool. Soc. 1867, p. 303, — by the 

 different dentition of the aperture ; of the latter I found about 40 

 specimens, to all appearance full grown and in first rate condition, 

 some of them, to my mind, very old specimens, in none of them were 

 there any signs of any teeth whatever within the outer margin of 

 the aperture ! Of the Bourbon species, I only found 5 specimens, 

 one evidently young, the other 4 full grown and all showing the 

 peculiar characteristics pointed out in my description. Still the 

 resemblance is so striking, that I think no naturalist would hesi- 

 tate to avow, that they must at no very remote period have had a 

 common origin ; there is, indeed, just the chance that at Mauritius 

 a similar variety may exist, but, from the number of specimens I 

 found there, I doubt it exceedingly. I have, however, written to Mr. 

 D u p o n t at Mauritius to ask him to kindly examine all he can 

 possibly procure of this species, and to see if he can find any trace of 

 the apertural teeth, which give such a different appearance to my 

 V. incerta. 



31. Tornatellina (Septinaria) cernica, Bens.,, Ann. Mag. 

 1851, p. 255. 



This interesting shell is perfectly identical with the Mauritian 

 form, described by Benson, I found it, at a considerable height, 

 with Vertigo Borloniea. 



