BITTIUM. 157 



B. FURVUM, Watson. PI. 31, fig, 27. 



Clathrate by 12-15 narrow ribs, and three narrow spiral riblets, 

 the intersections nodulous, the wide interspaces with decussating 

 microscopic striae, whorls slightly shouldered, body whorl with 

 several spiral ridges below the middle ; dark chestnut colored. 



Length, 27 mill. 



Sydney, N. S. Wales. 



B. XANTHUM, Watson. PI. 30, fig. 24. 



Less shouldered and not quite so stout as the preceding species, 

 with about 18 ribs, base longer and more attenuated, no microscopic 

 striae ; shell thin, ochraceous. Length, 3'5 mill. 



Torres Strait, N. E. Australia* 



B. PERPARVULUM, Watson. PI. 31, fig. 29. 



Shell only about half the size of B. furvum, but so close to it in 

 form and sculpture that I suspect that it will prove a minor form of 

 that species. The small differences are comparative only and can 

 be seen by inspecting the respective figures. Yellowish, or pale 

 chestnut, becoming nearly white below, sometimes chestnut or white 

 throughout. Length, 1'5 mill. 



N. E. Australia to Sandwich Is. 



B. LEUCOCEPHALUM, Watson. PI. 31, fig. 30. 



About 12, rounded ribs, with wider interspaces, crossed by three 

 narrow spiral ridges, the intersections nodulous, whorls a little 

 shouldered as in the preceding species, but not so high, base and 

 aperture also shorter ; yellowish or whitish. Length, 2*5 mill. 



Off Honolulu, Sandwich Is. 



Very like the preceding, with wider, fewer ribs and shorter base. 



B. PORCELLANUM, Watson. PL 31, fig. 28. 



Whorls slopingly shouldered above and below, the wide, flat- 

 tened middle space only bearing distant narrow longitudinal ribs, 

 base of body whorl with three spiral ridges, porcellanous white and 

 glossy, apex yellowish chestnut with a whitish tip. 



Length, 3'75 mill. 



Cape York, N. E. Australia. 



Section CERITHIDIUM, Monts., 1884. 



B. SUBMAMILLATUM, Rayneval. PL. 29, fig. 84. 



Whorls 12, convex, with deep suture, with eight longitudinal 

 ribs and much wider interspaces, crossed by five revolving riblets, 



