30 rROCEEDIXGS OF THE ACADEMY OF [Feb., 



I. — Si)ire more or less convex or low-couic; perij)licrv angular or 



cariuate. 



a. — Basal lip produced forward beyond the outer and upper 



margins ; periphery angular above ; whorls 5f , closely 



coiled ; upper surface diUl, striate, base glossy. 



h. — Spire but slightly convex. Alt. 2.1, cliara. 4.3 mm., 



H. sinuosa. 

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



3.1 mm., H. eutheca. 



a}. — Aperture normally oblique, the outer and upper margins 

 projecting forward of the basal. 

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

 phery merely angular. Alt. 2, diam. 4.6 mm., 



M. hypolia. 

 6\ — Base opaque, finely ribbed, like the upper surface; 

 periphery acutely cariuate. 

 c. — Biconvex; Avhorls 4J to 4|-. Alt. 2.2, diam. 



4 mm., H. nesiotlea. 



c\ — 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 cariuate, 

 concave below the keel, imi)erforate, 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, 



II. opercul'ma Old. 



