1888.] NATURAL SCIENCES OF PHILADELPHIA. 21 



similarity of shell-types would seem to indicate that, if ever separate, 

 they must have been united before the development of molluscan 

 life ; otherwise we should expect to find the types of East and West 

 Maui differing as much from each other as do those of Maui and 

 the contiguous islands of Molokai and Lanai." 



" Molokai. The distribution of Achatinella on this island pre- 

 sents some new features not observed on any other island. The 

 island is forty miles long with a width of only seven miles, it is 

 about one-third the size of Oahu, and like it has a mountain range 

 extending nearly thirty miles through its length. The range is fur- 

 rowed on each side by deep valleys. Some of these mountain 

 gorges are very wide and cut deep into the narrow axis of the island. 

 The larger ones have proved an effectual barrier to the migration 

 of the shells. The island is thus divided into three natural sections, 

 and each section retains its own peculiar species without intermin- 

 gling with those of the next section." " Molokai furnishes 25 de- 

 scribed species which are about equally divided between the three 

 sections of the island, these shells exhibit more variety of form and 

 color than those of Maui, and have peculiarities which separate 

 them entirely from types of other islands." 



" Lanai. Thi» is the smallest and most arid of the shell produc- 

 ing islands. Its area is 100 square miles, of which probably not 

 over one tenth is suited for the support of mollusks. The island is, 

 however notable as the home of A. magna Adams, the largest shell 

 of the whole Achatinella family. Specimens in our cabinet measure 

 I5 inches long, the whole number of species of Achatinella on Lanai 

 is 13, and they exhibit peculiarities of type." 



" Kauai. This is the oldest and most verdant island of the group. 

 It lies to the west of Oahu, and is separated from it by a channel 

 wider than occurs between any of the other islands. Its extensive 

 forests, luxuriant vegetation and moist climate render it peculiarly 

 adapted for the abode of Achatinella ; and one would naturally ex- 

 pect to find here a larger, and if possible, higher development of the 

 family. But we are doomed to disappointment, the island yields no 

 arboreal species, the shells are terrestrial, and those classed with 

 Achatinella belong to the plainest forms of the Amastra and Lepta- 

 chatina groups; 5 species to the former and 18 to the latter. 

 Kauai, however, does furnish a very peculiar and interesting group 

 of large terrestrial shells, remarkable for their elongate turretted 

 form. The generic name of Carelia has been provided for the group; 



