Original Descriptions of AcJiatinclla. 129 



When extended, two-thirds as long as the shell. — Xewc. (Ann. 

 Lye. Xew York, vi, p. 311. 



Hab. Mapulehu.— Bald. 



308. Achatinella citrina Pfeiffer. 



A. citrina Pfr. Rve. Icon. Conch. Achat., London, 1S30. pi. v. fig. 33. 



Shell elongately conical, sinistral, spire somewhat accuminated, 

 whorls rounded, finely striated, the last finely obsoletely keeled, 

 columella much twisted, two-plaited, aperture rather small; bright 

 citron 5'ellow. 



Hab. Kalae to Waikolu. — Bald. 



209. Achatinella helvina Baldwin. 



A. helviua Bald. P. Acad. Phil., 1S95, p. 227, pi. xi, fig. 30. 



Shell sinistral, imperforate or subperf orate, sometimes nar- 

 rowly and deeply perforated, rather thin, elongately conical, apex 

 rather acute; surface scarcely shining, covered with very fine in- 

 cremental striae; nuclear whorls smooth; color uniform white or 

 dingy yellow, with a few black markings on the upper whorls; 

 whorls 6 1-2, lightly margined above, convex; suture deeph' im- 

 pressed; aperture a little oblique, oval, white, with the tint of the 

 outside; peristome simple, thin, margins connected with a thin 

 orange-yellow callus; columella biplicate; the terminal plication a 

 thin, oblique lamellar plait, the inner one less prominent, tortuous, 

 of an orange-yellow color. Length i8, diam. lo mm. 



Animal extended in motion as long as the shell. Mantle and 

 foot above and below ver\- light brown. Tentacle very dark slate, 

 with a sprinkling of slate on the sides of the foot. Posterior por- 

 tion of foot very tapering and thickly studded with minute red 

 spots. A remarkably prolific species; 4 or 5 embryonic shells in 

 successive stages of growth often observed in the oviducts. A jaw 

 is present and the dentition is the same as that of the Aniastra 

 species. The tooth formula of this species is 32.1.32X108=7020. 

 The central tooth is a little wider than usual. — Prof. Gwatkin. 



This shell differs from all its congeners in its strongly bipli- 

 cate columella, and the peculiar soft parts of the animal. The 

 typical forms are found in the small valley of Ohia on Molokai. 

 Departing from this locality on either side, modified forms without 

 the biplicate columella are somewhat common. — Bald. 



Hab. Ohia Valley, near Kaluaaha. — Bald. 



Occasional Papers B. P. B. M., Vol. III. — 9. 



