WAIANAE SPECIES. 339 



usually encircled with a black-brown line at the junction of 

 the two ground-tints, and often there are several additional 

 lines widely spaced on the base or sometimes above. A faint 

 sutural line may usually be discerned. Embryonic whorls 

 when unworn are cartridge buff, slightly darker near the 

 sutures, but not at the tip. The outlines of the spire are per- 

 ceptibly concave, the last whorl swollen. Lip moderately 

 thickened, white; columella very faintly rose-purple. 



Length 20, diam. 13 mm. ; 6% whorls. 



Length 18.7, diam. 12.2 mm. ; 6y 2 whorls. 



Oahu: Kahuku, at an elevation of 1,500 to 1,750 ft. (L. A. 

 Thurston). Cotypes in coll. A. N. S. and Bishop Mus., from 

 Mr. Thurston 's collection. 



This race is one of the most attractive of the "Apex" 

 group. While very distinct in appearance, its kinship with the 

 valida series is shown by the rare yellow-based form of cine- 

 rosa, which however does not have the turgida-like shape of 

 the Kahuku form. 



Mr. Spalding informs me that there are black and white 

 mutations of this Kahuku race. 



Species from the Waianae Range. 



Affinities and origin. The species A. mustelina is now con- 

 sidered by Hawaiian conchologists to include all the Waian- 

 aean forms of the typical section of Achatinella (Apex), with 

 the possible exception of A. concavospira. In this wide sense 

 the species inhabits the whole range, where conditions are suit- 

 able. It is often very abundant. It is related to A. decora 

 Fer. and A. valida Pfr. of the Main Range. Some specimens 

 of decora are hardly separable from mustelina, but in the 

 main, the variations of the two differ rather widely. A. decora, 

 valida and mustelina appear to be slightly differentiated forms 

 of a common ancestral species which lived in the western val- 

 leys of the Main range of Oahu. The migration to the Waia- 

 nae range may have begun in a late stage of the Pliocene, but 

 more likely in the Pleistocene. Up to historic time forests ex- 

 tended from range to range, and Amastra, Pterodiscus and 

 other forest snails of the two ranges mingled. The more an- 



