208 AMASTRA, OAHU. 



tdon. The post-embryonic whorls are more convex, roughly 

 and irregularly sculptured with growth-wrinkles, which be- 

 come quite coarse on the back of the globose last whorl. Aper- 

 ture is slightly oblique, with a very thin white lining. Lip 

 sharp and thin. Columellar lamella small, thin, white and 

 quite oblique. Length 13, diam. 9.1, aperture 7.8 mm. ; 5% 

 whorls. 



Oahu : Mokuleia, Waianae mountains ( Irwin Spalding) . 



A thin shell of unusually swollen shape. In contour it is 

 not unlike some of the small, sub globose individuals of A. 

 tristis, such as occur in Moanalua, but it differs by lacking a 

 dark deciduous outer layer of cuticle and in the sculpture of 

 the embryonic whorls, so that the relationship cannot be 

 thought close. Its relationships are not clear to us. No other 

 described Oahuan shell resembles it. The type, to be de- 

 posited in the Bishop Museum, is not fully adult. 



Section PARAMASTRA Hyatt & Pilsbry. 



These are pyramidal or more or less turrited forms, usually 

 with the spire straight or concave-sided ; whorls rather numer- 

 ous, 6 to 8 ; shell often spirally banded or with many lines ; 

 cuticle often without a dark, deciduous, outer layer; embryo 

 very finely striate vertically ; colors variable, often variegated, 

 frequently resembling the Achatinellina rather than the usual 

 pattern of Amastra, probably in consequence of an adapta- 

 tion to arboreal life in some forms. 



Type A. spirizona. 



The distinction between these shells and the rub ens group 

 is not always clear, as there seem to be some intermediate 

 species. The group is confined to Oahu. It is much more 

 fully developed in the Waianae Range (seven species) , whence 

 two species have migrated to the Main Range, there to give 

 rise to two species special to the eastern range, A. porphy- 

 rostoma and A. turrit ella-, both of these are still connected 

 with the parent forms (porphyrea and spirizona nigrolabris) 

 by more or less intermediate shells. 



The shells of this group have a tendency to develop a second 

 <jolumellar fold above the usual lamella, as in the Lanaian 



