Extinction, of Organic Beings. 477 



One species, however, the " Nanina vesicula," found by 

 myself between Neemuch and Mhow, and subsequently dis- 

 covered by my friend Mr. W. H. Benson in the Rajmahl 

 range, seems alike to defy the heats of the provinces and 

 the winter of the hills, ascending even beyond the height of 

 ten thousand feet above the sea. It ranges therefore over 

 the central and western tracts of the Bengal Presidency, and 

 occurring in profusion along the verge of the hills at Mansir 

 Debi, mounts to Subathoo, Simla, and Huttoo mountain, 

 preserving everywhere precisely the same habits. 



Another species, the " Nanina vitrinoides" of Deshayes, 

 inhabiting the Rajmahl range, and extending also to the 

 western frontier, advances upwards only to Subathoo and its 

 neighbouring valleys, passing at Simla into a strong variety, 

 possessing the same form, and partaking of the same habits 

 and general economy. 



" Succinea crassiuscula" of Benson has also a wide range, 

 and is apparently to be met with throughout the provinces, 

 occurring abundantly, according to the above gentleman's 

 observations, in the compound of the Asiatic Society's rooms 

 in Calcutta, extending through Bahar and Allahabad to the 

 western frontier, and advancing to the hills as high as 

 Subathoo. 



Yet although we find some species common to the plains 

 extending far into the hills, there is nevertheless a well 

 marked line of elevation beyond, which the welfare of the 

 general number forbids them to pass. 



Thus while " Nanina vesicula" is found roaming through 

 the hills apparently at all elevations up to 10,500 feet, other 

 species which in the plains of India are found in company 

 with it, and at the same seasons, never mount beyond a third 

 of that height, confining themselves to the warmer valleys at 

 about three to four thousand feet above the sea. 



Among these are " Nanina vitrinoides" and " Succinea 

 crassiuscula," which around Subathoo are found in company 



3 Q 



