DENTALIUM. 13 



D. DUODECIMCOSTATUM Brazier. 



Shell straight, white, thin, shining, smooth, six-sided, having two 

 longitudinal rounded ribs, one on the edge of each square, from the 

 center between the interstices one fine rib extending to the base, 

 making in all 12 ribs; apex tapering, entire, with minute perfora- 

 tion ; aperture large. Length 11 lines, diam. of apex T, base 1 line 

 (jra*.>. 



Darnley Island, Torres Straits, 30 fathoms, sandy mud (Chevert 

 Exped.). 



D. duodecimcostatam BRAZ., P. L. S.N.S. Wales, ii, p. 56 (1877). 



Only one specimen found. It differs from anything at present 

 known. The shell is six-sided, the base with twelve ribs, and from 

 the center to the apex six, with the interstices smooth (Brazier). 



D. FILOSUM Broderip & Sowerby. 



Shell slender, thin, white ; with 8 longitudinal threads and very 

 close transverse striae. Length 2'6, diam. 0'2 inch (B. & &). 



Tenasserim, on shore. 



D.filosum B. & S., Zoological Journal, v, p. 48 (1830-1832). 



Distinguished from D. octogonum by its much more slender shape 

 and its thinner shell. Instead of the eight angles of that species it 

 has eight distinct, raised, longitudinal threads. Three specimens of 

 this fine species were lately brought to England by Mr. Hay, who 

 himself picked them up on the coast of Tennasserim (B. & S.). 



It is somewhat peculiar that this apparently distinct and large 

 species has not been noticed by any author since its original descrip- 

 tion. Compare D. javanum. 



D. STRIGATUM Gould. PI. 5, figs. 69, 70. 



Shell considerably curved, solid, rapidly tapering ; surface luster- 

 less, white with several irregular transverse grayish-translucent 

 bands. Sculpture of IS strong and rather sharp ribs continuous from 

 end to end, separated by wider deeply concave intervals; no trace of 

 interstitial riblets ; intervals and ribs longitudinally very finely stri- 

 ated. Aperture hardly oblique, circular, the peristome strongly 

 scalloped by the ribs, which are represented by grooves within the 

 tube. Anal orifice much smaller than the truncated apex, oblong, 

 with a raised ledge at each side. 



Length 15'2, breadth at aperture 2'4, at apex 0'9 mill. 



Length 18, breadth at aperture 3 mill. 



False Bay, Cape of Good Hope (N. Pacif. Expl. Exped.). 



