INTRODUCTION. 



Evolution and Zoogeography of the Amastrince. 



I. Achatinellidae the new incarnation of an ancient phy- 

 lum. 



II. Geologic and topographic data bearing on the evo- 

 lution of Achatinellidas. 



III. Means of dispersal. 



IV. Centers of radiation. 



V. Systematic and geographic relationships of genera and 



sub genera, 



VI. Probable sequence of events determining evolution of 

 the Hawaiian fauna. 



I. 



The Achatinellidce are a branch of the primitive and an- 

 cient group Orthurethra, a group comprising most of the 

 land Pulmouata of the Pacific islands, including also the 

 families Partulidcs, Tornatellinidce and Pupillida?. Such evi- 

 dence as we have leads us to infer the existence of Orthure- 

 throus snails in the Pacific for a very long time, probably 

 since the Palaeozoic. The total absence of modern types of 

 land Pulmonata in these archipelagos, as I have elsewhere 

 argued, is against the view that their snail faunas are solely 

 due to waifs from the continents, adventitiously stranded 

 from time to time. 



By analogy with generic and family groups of known age 

 in Europe and America, it seems likely that the Achatinellidtf 

 were already differentiated as a family before the beginning 

 of the Tertiary. Yet the rather close relationship of the genera 

 of Amastrince, and the even greater proximity of the genera 

 of Achatinellina?, seem to tell of a rather sudden expansion 



(xi) 



