716 ON THE MOLLUSCA OF THE ' CHALLENGER ' EXPEDITION. 



colour white, glossy. Sculpture. The whole substance of the shell 

 is faintly marked with remote spiral threads, and the surface is 

 very faintly scratched with closer microscopic striae. The whorls 

 are bluntly angulated in the middle, and the last is so besides at 

 the base below the periphery ; this angulation meets the outer lip. 

 The second and third whorls have two or three strong spiral 

 threads. Longitudinals — there are very many, close, unequal, 

 very oblique, hair-like lines of growth, of which the strongest rise 

 in close-set, iufrasutural puckerings, which on the third whorl 

 resemble small beads. Colour. There is a glossy, thin, ivory-white 

 calcareous coat over a brilliant pearly white layer. JEpiderr)iis. 

 On the one living specimen there is an excessively thin tenacious 

 brown layer, which may possibly be only an accidental deposit. 

 Spire high, fine-pointed. Apex blunt, the smooth round embry- 

 onic li whorl scarcely projecting. Whorls 6, of rapid increase, 

 tumid, the penultimate especially rising swollen out of the suture, 

 the base is a little flattened. SutureliuQax, not impressed, a little 

 coarse, slightly marginated by the up-lap of the siicceeding on the 

 preceding whorl and the slight tumidity caused by the iufrasutu- 

 ral puckerings. Mouth very oblique, round, with a soft pearly 

 nacre all round. Outer lip very slightly descending, thick, bevel- 

 led outwards to a sharp edge. Pillar-Up. There is a broad, thin, 

 hyaline pad spread over the body and connecting the outer lip 

 and the pillar, which is broad, thick, shallowly excavated, with a 

 slight external median horizontal tooth or ridge ; the edge is 

 reverted and closely appressed. Operculum small, thin, calca- 

 reous, flat, convex on the inside, where it shows 7| whorls ; the 

 last whorl close to its end begins suddenly to enlarge. Teeth 

 distinctively those of the family as represented by Loven (see 

 Trochus or Phasianella), there being endless rows of innumerable 

 minute crooked uncini, with several (probably eleven) hooked 

 and serrated central rasps, but in their confused dried-up condi- 

 tion it was impossible more minutely to identify them. H. 0'27. 

 B. 0-25, least 0-23. Penultimate whorl 0-09. Mouth, height 

 0-13, breadth 0-12. 



There is in the B.M. a species marked " Collonia marginata, 

 Lam.," which in colour and form more than any other resembles 

 this ; but that is lirated, is rounded on the base, is toothed on the 

 outer lip, and has not the angulation in the middle of the whorls. 



