118 THE NAUTILUS. 



2 forming the large nepionio shell. Last whorl wide, strongly car- 

 inate, a little sunken above and below the median keel, scarcely de- 

 scending in front, convex beneath. Aperture oblique, wide, the lip 

 obtuse, expanded above and outwardly, reflexed and thickened be- 

 low. Alt. 14 to 15^, diam. 23 mm. 



Hahajima, Ogasawara (Mr. Y. Hirase, no. 805). 



An exceedingly distinct species, like a thick Plectotropis. It is 

 quite unlike the larger carinate species Mandarina Pallasiana. 



Microcystina hahajimana n. sp. Shell very minutely perforate or 

 closed, depressed subglobose. Amber colored, translucent, brilliantly 

 glossy, smooth except for some very slight growth-wrinkles. Spire 

 quite convex. Whorls 5, nearly flat, the sutures but lightly im- 

 pressed, narrowly margined. Last whorl faintly angular in front, 

 convex beneath, impressed in the center. Aperture lunate, the 

 peristome simple and acute ; columella thickened above and bluntly 

 toothed. Alt. 4, diam. 6^ mm. 



Hahajima, Ogasawara (Bonin Islands). No. 803 of Mr. Hirase's 

 collection. 



Genus HIRASEA nov. 



Small disc-shaped or biconvex, perforate shells, pale and of nearly 

 uniform tint, finely rib-striate, the aperture crescentic, the peristome 

 contracted, thickened with a very heavy callus rib within. Type 

 Hirasea sinuosa. 



This genus belongs apparently to the Zonitidce, or possibly to the 

 Endodontidce. It has some resemblance in the thick lip-rib to 

 Brazieria or Microphynra, but there is no parietal barrier. The 

 Philippine groups Pliotropis and GJyptoconus have some similar 

 characters, but they are thin shells with no lip-rib. The species 

 now known may be distinguished as follows : 



a. Upper margin of the lip drawn back, the basal margin project- 

 ing beyond it. Spire low, composed of 5| very narrow and 

 convex whorls, the last angular at the shoulder, very con- 

 vex beneath, perforate ; aperture narrowly crescentic ; lip 

 expanded and arched forward in the middle below, retracted 

 at the upper termination. Alt. 2.1, diam. 4.3 mm. Haha- 

 jima, Ogasawara (Hirase, no. 802). H. sinuosa, n. sp. 

 a 1 . Aperture normally oblique, the upper margin projecting for- 

 ward ; form biconvex. Whorls 4|, with an acute, com- 



