372 HYATT: GENEALOGY OF ACHATINELLID^. 



more closely associated have faunas derived from each other 

 in substantially similar succession, and by what seemed to be 

 a very recent migration. These results led naturally to the 

 conclusion that Kauai was the oldest, and that the others had 

 risen above the waters in the succession indicated by the 

 faunas. This was sound insofar as the age could be deter- 

 mined by the relative time at which each island had become 

 covered sufficiently by vegetation to be suitable for the exist- 

 ence of the more primitive forms of land shells. 



The fact that Kauai contained the oldest fauna of this 

 group has already been stated by Baldwin and Gulick, and 

 it has been generally admitted that each island had its dis- 

 tinct fauna, and also that each of the valleys, in Oahu es- 

 pecially, was apt to have some peculiar varieties or species. 



Turning then to the geology, for more information, I found 

 that Dana, Button, and others were in substantial agreement 

 with my conclusions, basing their opinions upon the topo- 

 graphy of the different islands and the comparative age of 

 extinct and active volcanoes and lavas. This analysis was 

 also carried into the separate parts of different islands. 

 Thus I became convinced that so far as the migration of shells 

 were concerned the western or Waianae range of Oahu was 

 more recent than the eastern or Konahuanui range, and in 

 Maui that the western mountain-peak of that island, Mt. 

 Kukui, was older than the eastern region around the base of 

 Mt. Haleakala. The last deduction has been confirmed by 

 geologists, notably Button, but the first remains thus far 

 undecided. So far as our present knowledge goes there is 

 then in these islands the most remarkable case yet known of 

 the evolution of a succession of -closely connected homogenetic 

 faunas which have evolved without serious interference from 

 the invasion of foreign importations. The Achatinellid(z 

 came to the island of Kauai, according to my deductions, 

 obviously before other islands had become habitable ; and they 

 came in the shape of certain shells of very distinct primitive 

 structure whose descendants are still found living in that 

 field. Then all of the members of that family group were 

 evolved from this island through the others in determinate 



