88 DENTALIUM-GRAPTACME. 



translucent white, with opaque white wavy lines (like those on the 

 silk goods known as moire antique) encircling the shell with zig-zags, 

 whose successive irregular bands (08 mill, apart in the middle of 

 the shell) are sub-parallel with one another, and gradually become 

 more slender and further apart toward the ends. In a specimen 

 13 mill, long, there were about fifteen of these bands, each with 

 about ten or twelve angles. Length 13 mill., oral diam. 1*2 mill., 

 anal 0'37 mill. (Dall). 



11 This species is more acute than D. taphrium of the same size, and 

 the moire antique effect is of a much more prominent and zig-zag 

 pattern. In D. taphrium the sculpture is also coarser. A some- 

 what similar effect is observable on the younger portion of D. 

 aculeatum Sowerby, which is otherwise very different. The Indo- 

 Pacific D. nebulosum Deshayes also exhibits it. The sculpture is 

 entirely independent of these differences of opacity, which at first 

 one finds it difficult to realize." (Dalt). 



D. CIRCUMCINCTUM Watson. PL 8, fig. 26. 



Shell very long and narrow, very slightly bent, and that almost 

 entirely above; a very little flattened on the concave curve, so as to 

 be slightly trigonal ; white, opaquely porcellanous, a little glossy, 

 not thick but strong. Sculpture : closely and regularly girt round, 

 elliptically with scratch-like puckerings in the lines of growth, of 

 which there are about 55 in the tenth of an inch. Longitudinally 

 striped with fine ribs, of which there are from 17 to 20, sharp and 

 well defined by still broader furrows toward the apex, but down the 

 shell these increase in number and steadily decrease in definiteness 

 till they only show as a feeble system of lines on the rounded sur- 

 face. At the apex there is on the convex curve a ragged irregular 

 fissure about O'l inch long. Length 1'93 [48 mill.], breadth at 

 mouth 013 [3-25 mill.], at apex 0'02 inch. ( Watson). 



Setubal 470 fms. ; Sombrero /., W. Indies 450 fms. ; off Bermuda 

 1075 fms. ; Pernambuco 350 fms. (Challenger). 



D. circumcinctum WATS., Journ. Lin. Soc. Lond., xiv, p. 513 

 (1879) ; Chall. Rep., p. 7, pi. 1, f. 7. 



As compared with D. semipolitum Sow., this is a longer, straighter, 

 more attenuated shell, with striae stronger, blunter, and more per- 

 sistent. It is not unlike D. antillarum d'Orb., in texture and in 

 size, but is much straighter and narrower, and the early ribs are 

 much finer and fewer. It is intermediate in form between D. 



