188 HELIX-RHAGADA. 



The spire is low-conoidal, composed of a little over 5 whorls, sep- 

 arated by distinctly impressed sutures ; the last whorl is rounded at 

 the periphery or somewhat obtusely angled at its origin and slowly 

 descending in front. The aperture is half-round, white within, 

 rather oblique, peristome thick, blunt, the outer lip a little expanded, 

 colurnellar lip dilated in a thick pad of callus covering the umbilicus 

 and adherent around it. There is no depression at the place of the 

 umbilicus. 



Alt. 15, greater diam. 21, lesser 18 mill. 



Alt. 16, greater diam. 23, lesser 18 mill. 



Nicholas Bay to Mermaid Strait, northwest Australia. 



H. convicta Cox P. Z. S. 1870, p. 171, t. 16, f. 6. VON MARTENS, 

 Monatsberichte der Koniglich Preussischen Akademie der Wissen- 

 schaften zu Berlin, 1877, p. 272, t. 1, f. 6, 7. PFR. Mon. Hel. Viv. 

 vii, p. 323. 



Larger than the other species, solid, compact, imperforate. Fig. 

 65 of pi. 14 is from the original one of Cox ; this (typical) form is 

 pale yellowish-white with two narrow brown bands, one near the 

 center of the whorls, the other immediately below the suture. Figs. 

 7, 11 of pi. 30 represent the slightly differing form described by Von 

 Martens, with sharply denned peripheral band of reddish-brown, 

 and a paler yellowish one at the suture ; the lip not thick ; 'ground- 

 color a shining white. The specimen described by me and figured 

 on PL 35, figs. 8, 9, 10, is thick, heavy, white, with a scarcely nutic- 

 able translucent, narrow peripheral band. The lip is very thick, 

 ivory-white. 



H. PLECTILIS Benson. PL 35, figs. 16, 17, 18. 



Shell depressed-globose, nearly covered umbilicate, white, rudely 

 wrinkled above (except the rather prominent obtuse apical whorl 

 which is smooth), radiately striate below; last whorl very deeply 

 deflexed in front ; aperture nearly circular, the ends of the lip ap- 

 proaching. 



It is a compact little shell, chalky- white, solid, opaque. The sur- 

 face has coarse, irregular, oblique wrinkles above, in places inter- 

 .rupted, forming low tubercles ; this coarser sculpture is covered by 

 a minute granulation, visible only under a lens. The base of the 

 shell has rather coarse, low wrinkles of growth. Whorls 4J, convex, 

 separated by impressed sutures. The earlier H or 2 whorls are 

 smooth. The last whorl is very obtusely subangular at its origin, 



