CLASSIFICATION. Xlll 



Partulina montagui is a very distinct species, but not in the 

 least primitive in character. Two other extinct forms are 

 distinguishable races of living species, while the other three 

 found fossil do not seem to differ from modern shells. 



Further extinct species are to be expected in comparatively 

 high beds, such as the Manoa and Palihoukapapa forest de- 

 posits. Many such must exist, and they may afford a good 

 deal of light on such obscure questions as the part taken by 

 Partulina in the ancient Oahuan fauna. 



CLASSIFICATION OF ACHATINELLHXE. 



It has been stated above that the genera and subordinate 

 groups of Achatinellida are based entirely upon characters 

 of the shell. The soft anatomy, so far as known, is practically 

 alike in all. The genera are not groups of much systematic im- 

 portance not more I should say, than the "sections" estab- 

 lished in my monograph on Partula; but they are obviously 

 natural groups, which have been found useful in dealing 

 with long series of species. 



The family divides primarily into two groups, Partulina 

 and Achatinella. By their coloration and sculpture, New- 

 combia, Perdicella and Baldwinia are obviously derivatives 

 of Partulina. The Partulina group is more numerous in 

 species and far more varied in structure than Achatinella, 

 which consists of three very closely related sections. Ebur- 

 nella is a group of uncertain affinities, but apparently linked 

 to Partulina by certain species of Maui and Lanai. The ap- 

 proximate relationships of the groups are represented in the 

 following diagram. 



Newcombia 



Baldwinia 



Partu 

 Partulina s. str. 



Perdicella 



inella | 



Eburnella Achatinellastrum 



Bulimella 



(Partulina') (Achatinella) Achatinella s. str. 



i 



Ancestral 

 Achatinellid 



