80 Remarks on Mollnsca and Shells. 



The little island of Metia, or Aurora Island, to the north- 

 eastward of Tahiti, is one of peculiar interest. It is a coral 

 island, which has been elevated 250 feet or more, and has no 

 other high island anywhere near it. On it were found four 

 small land-shells belonging to three genera, viz., Helix perte- 

 nms, Helix dccdalea, Partula pusilla, and Helecina trochlea. 

 None of these were found upon any other island. They seem 

 to have originated there after the elevation of the island, and 

 have a significant bearing upon the question of local and pe- 

 riodical creations in comparatively modern times. 



As the genus Partula is characteristic of the groups just 

 south of the equator, so Achatinella is the characteristic 

 shell of the Sandwich Islands. Closely connected as the 

 islands of this group are, they each have their peculiar forms 

 of land-shells ; and, as the southern islands bear evidence of 

 greater age than the northern ones, we may infer that, within 

 these narrow limits, we have evidence of the appearance of 

 some species subsequent to the existence of others now liv- 

 ing. On the island of Kauai, the oldest of the group, we 

 have Achatina adusta smdpyramidata, a form which does not 

 appear on the other islands ; the Achatinella} are chiefly of 

 the elongated glabrous form, which I have grouped under the 

 name Lepiachatina ; the Helices are planorboid and multi- 

 spiral. On Molokai, the species of Achatinella are large and 

 beautiful, and peculiar in their form and colouring. On Maui, 

 the Helices are small and glabrous, with some very curious 

 hispid and ribbed species, with lamella) within the aperture. 

 On Oahu, the species of both Helix and Achatinella are simi- 

 lar to those on Maui. On Hawaii, Succinea seems to prevail 

 in larger proportion than on the other islands, while Acha- 

 tinella, which occurs so abundantly on all the other islands, 

 either does not occur at all, or but very rarely. 



