DENTALIUM. 15 



D. curium -? , Sows., Thes. Conch., iii, p. 100, pi. 225, f. 62, under 

 figs. 47, 48 (1860) ; Couch. Icon., xviii, pi. 6, f. 42 (1872). 



Short, pale brown, finely striated, strongly arched, rapidly increas- 

 ing ; apex attenuated and acuminated ; apical fissure small. (Sowb.). 



D. PORCATUM Gould. PI. 6, fig. 80. 



Shell moderate, chalky, more or less ruddy at the apex, well 

 curved, with 12 delicate longitudinal sulci, increasing to 20. Length 

 20, diam. 2-5 mill. (Old.). 



Hongkong Harbor, China (N. P. Expl. Exped.). 



D. porcatum OLD., Proc. Bost. Soc. N. H., vii, p. 166 (1859) ; 

 Otia Conch., p. 119. Sows., C. Icon., xviii, pi. 7, f. 47. 



D. BISEXANGULATUM Sowerby. PI. 2, fig. 25. 



Shell well curved, solid, moderately stout, the length about 11 or 

 12 times the greatest diameter; white. Sculpture of about 12 (11 

 to 13) strong longitudinal narrow ribs, about a third as wide as the 

 concave intervals, which are ribless or show a weak median thread 

 on the convex side (or occasionally all the intervals except one or 

 several on the concave side have low median threads) ; growth-strise 

 fine and superficial. Aperture a trifle compressed laterally, strongly 

 angulated by the projecting ribs on the concave margin, but much 

 less so in adult shells on the convex margin. Anal orifice rounded, 

 with a wide, shallow notch on the convex side. 



Length 68, length of aperture 6'5, breadth 6 mill. ; height of arch 

 from chord 10 mill. 



Length 72, length of aperture 6'2, breadth 6 mill. ; height of arch 

 from chord 11 '5 mill. 



Java (Sowerby) ; Singapore (Archer) ; Yokohama, Japan (Loo- 

 mis) ; Gulf of Suez (MacAndrew) ; Torres Straits and vicinity, 8-30 

 fms. (Chevert Exp.). 



D. bisexangulatum SOWB., Thes. Conch., iii, p. 102, pi. 223 f. 8 

 (1860), and in Conch. Icon., xviii, pi. 3, f. 15 (1872). COOKE, 

 Ann. Mag. N. H. (5), xvi, p. 273. BRAZIER, Proc. Linn. Soc. N. 

 S. Wales, ii, p. 57 (1877). 



So far as our material goes, there are oftener 11 than 12 ribs ; and 

 the development of an intermediate thread in each space over the 

 greater part of the shell is occasional though probably exceptional. 



The specimen from Yokohama which I refer to this species came 

 with a series of D. octangulatum. It is 11-ribbed, and measures, length 



