6 N'c'w Species of Aviastra. 



tapering gradually to the base. Aperture large, very oblique, 

 subquadrate in outline, with a very convex outer margin, and 

 furnished with a thick broad lip-rib, obtusely angulate at the base 

 of the columella and having a thick parietal callus. Columellar 

 fold basal in situation, rather strong, subtransverse, terminating 

 abruptly back of the columellar margin. Umbilicus small, cleft- 

 like nearly closed by the thickened callus of the outer margin of 

 the columella. 



Length 11.5, diam. 6.9, apert. 5.5 mm.; 6 whorls. (Holotype) 



Kauai: (Judd). 



Holotype No. 41,995, Bishop Museum. 



This species is represented by the single type specimen in the 

 collection of the Bishop Museum and two or three additional 

 specimens in the Judd collection. It is entirely unlike anj^ other 

 species of Cycl aviastra from Kauai. Its nearest relative appears 

 to be A. 7unbilicata from Oahu. From this species it is most easily 

 distinguished by its flatter whorls, greater proportional width, and 

 broad aperture. 



A. thurstoni, n. sp. 



PI. B. Fig. 2. 



The shell is narrowly perforate, accuminately turreted, rather 

 thin ; spire with convex outlines, slowly tapering to the rather 

 acute summit. The surface is rather strongly and almost regularly 

 plicated, the plicae are not sharp and gradually diminish in 

 height towards the apex, stopping abruptly at the 2)2 whorl. 

 Whorls seven, the embryonic, convex, at first increasing rapidly 

 then more slowly, almost smooth, very faintly striate. The fourth 

 contracted, less convex than the remaining whorls; the last long, 

 tapering towards the base, indistinctly angulate about the margin 

 of the perforation. Umbilicus contracted slightly at its mouth, 

 compressed, narrow. Aperture somewhat oblique, subrhomboidal, 

 furnished just within the outer lip with a thick blunt callus. 

 Columella narrowly triangular. Columellar fold basal in position, 

 oblique, extending nearly to the margin. 



Length 14.4, diam. 6.3, apert. 5.5 mm. 



Oahu : Manoa, in excavation for Mr. R. Mist's house (Thurs- 

 ton, Oestergard and Cooke). 



Holotype No. 40,631, Bishop Museum. 



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