30 PROCEEDINGS OF THE ACADEMY OF [Feb., 



I. Spire more or less convex or low-conic; periphery angular or 



carinate. 



a. Basal lip produced forward beyond the outer and upper 

 margins; periphery angular above; whorls 5f, closely 

 coiled ; upper surface dull, striate, base glossy. 

 b. Spire but slightly convex. Alt. 2.1, diam. 4.3 mm., 



H. sinuosa. 

 b l . Spire low-conic; base very convex. Alt. 2, diam. 



3.1 mm., H. eutheca. 



a 1 . Aperture normally oblique, the outer and upper margins 



projecting forward of the basal. 



6. Base translucent, thin, polished; whorls 5J; peri- 

 phery merely angular. Alt. 2, diam. 4. 6 mm. , 



H. hypolia. 

 b l . Base opaque, finely ribbed, like the upper surface; 



periphery acutely carinate. 

 c. Biconvex; whorls 4 \ to 4|. Alt. 2.2, diam. 



4 mm., H. nesiotica. 



c 1 . Much depressed, the keel very acute; whorls 4. 



Alt. 1.6, diam. 4 mm., . . H. acutissima. 



II. Spire concave, the earlier whorls sunken ; periphery rounded. 



a. Disk-shaped; rich brown, and densely, minutely rib -striate 



above and at the periphery, becoming polished and 



somewhat translucent beneath, whitish near the axis. 



Whorls 5, the last rounded at the periphery ; aperture 



lunate, the lip simple and acute in the specimens seen, 



which are probably not adult. Alt. 1.7, diam. 4 mm., 



H. biconcava. 



Another genus or subgenus, apparently allied to Hirasea, is re- 

 presented by one species sent from Hahajima, and by Helix oper- 

 culina of Gould, collected on Peel Island [Chichijima] by the 

 North Pacific Exploring Expedition, but not yet obtained by Mr. 

 Hirase. This group may be defined as follows : 



FAMETESTA subgen. nov. 



Shell disk-shaped, excessively depressed and acutely carinate, 

 concave below the keel, imperf orate, thin, minutely striate. Aper- 

 ture oblique, extremely narrow, the basal lip thickened within. 

 Type H. mirabilis. 



Two species are now known. Both are pale brown with 5 whorls. 

 They differ thus : 



a, Diameter three times the altitude, 2.5 x 7.5 mm. Chichijima 



H. operculina Gld. 



