HYATT: GENEALOGY OF ACHATINELLID^]. 391 



Achatinella. All of them have the surfaces, apices, and gen- 

 eral aspect of true Achatinellas. 



In these forms, therefore, outside of Molokai, there is a 

 constantly recurring tendency to imitate the thickened colu- 

 mella and apertures of Partulina, but this does not extend 

 to any alteration of the general aspect nor of the texture of 

 the surface as has been stated above, nor in the patterns and 

 colors, the colors being brilliant and banded throughout the 

 islands. 



The characters of the apertures have caused most authors 

 to include either all or part of these in the genus Partulina, 

 but the colors and forms are, it appears to me, conclusive in 

 favor of the theory of direct connection with the unques- 

 tionable Achatinellas of Molokai, and if this be true, it fol- 

 lows necessarily that the Bulimella apertures are simply 

 parallelisms with Partulina and have consequently neither 

 genetic nor taxonomic significance except within the limits 

 of the series itself. 



Achatinella nattii Bald, and Hart, has the typical apex and 

 general aspect of Achatinella in most specimens, but there 

 is a tendency in many shells to form a callous or shield which 

 often develops to be as large and well marked as in Partulina. 

 The same is true of the outer lip, that often becomes thick- 

 ened at the same time. So far as these characters are con- 

 cerned, this species or some of its varieties is a Partulina, 

 but all of the specimens have the apex and external surface 

 like Achatinella. All of these have either a uniform or 

 banded pattern in the young, never a cross-barred or zigzag 

 pattern. 



Partulinella marmorata series: This group consists of shells 

 having an apex similar to that of Achatinella in shape but 

 with heavier longitudinal ridges which also persist through- 

 out the later stages of the shell. The surfaces in later stages 

 are also apt to have persistent transverse ridges of growth 

 much coarser than in Achatinella and like the latter in that 

 the longitudinal ridges also persist and usually cross them 

 even on the last volution. The roughness of the shells is 

 therefore a marked characteristic just as it is in the Partulina 

 virgulata series. 



