DENTALIUM-OEVIDENTALIUM. 109 



double the length of the notch. D. bisinuatum also approaches D. 

 erectum Sow., Jr., but is smaller, more curved, and the posterior 

 notch is not so deep. (Andre). 



D. INSOLITUM E. A. Smith. PI. 22, figs. 56, 57. 



Shell slender, conspicuously arcuate, smooth, polished, subpellu- 

 cid, white ; with the tube hardly circular, being lightly flattened on 

 each side. Striated with very delicate growth lines, hardly slit at 

 the apex. Length 36, greatest diam. 2*5 mill. (Smith). 



Bay of Bengal, in 597 fms. (Investigator). 



D. insolitum SMITH, Ann. and Mag. N. H. (6), xiv, p. 168, pi. 4, 

 f. 17, 17a (Sept., 1894). 



The peculiarity of this species consists in its being a little com- 

 pressed, so that the tube is not circular. It is broadest along the 

 concave curve, which is not so round as the opposite side, and al- 

 most defined by lateral angles. (Smith). 



D. DIARRHOX Watson. PI. 3, figs. 36, 37, 38. 



Shell white (chalky), but porcellanous beneath the surface, 

 rather straight, with a considerable bend near the apex ; of rather 

 rapid expansion from a very fine apex. Sculpture : the whole sur- 

 face is faintly marked with scarcely impressed longitudinal lines of 

 very equal interval (about 0'0055 apart) ; transversely it is very 

 faintly scratched all over by very slight lines, which run elliptically 

 round the shell. The apex has a very narrow, slightly ragged fis- 

 sure, about 0'027 inch long, which lies unsymmetrically on the con- 

 vex curve. Length 0'6, breadth 0'09 inch. ( Watson). 



Animal : Mantle white, body pale yellow. Captacula many, fine, 

 long and equal, with small ovoid points. Foot and collar those of 

 a true Dentalium. 



N.-E. from New Zealand, lat. 37 34' S., long. 179 22' E., in 700 

 fms. (Challenger). 



D. diarrhox WATSON, Journ. Linn. Soc. Lond., xiv, p. 511 

 (1879) ; Chall. Kep., p. 4, pi. 1, f. 5. 



This differs from D. leptoskeles Wats., in being more curved and 

 more conical. It resembles in form the young of D. lubricatum 

 Sowb. " from Australia," but in that the transverse strise are much 

 less oblique, and the surface is "lubricate" and polished. (Wat- 

 son). 



