4 DENTALIUM. 



D. INTERSTRIATUM Sowerby. PL 1, fig. 15. 



Shell strongly arcuate, green, narrow ; primary ribs about 10, 

 with smaller ones in the interstices ; apex entire (Sowb.). 



fiohol, Philippines, (Cuming) ; Amboina. 



D. interstrialum SOWB., Thes. Conch., iii, p. 102, pi. 223, f. 7 

 (1860) ; Conch. Icon., xviii, pi. 2, f. 10. 



Kesembling D. aprinum, but with numerous interstitial striae 

 (Sowb.'). We have seen no authentic specimen of this form, but 

 from the description and figures would be disposed to consider it a 

 variety of D. aprinum with somewhat stronger interstitial striae than 

 usual. 

 D. JAVANUM Sowerby. PI. 4, fig. 49. 



Shell strongly arcuate, pale tawny or greenish, angulated by 8 

 ribs, the interstices wide and flat ; apical slit small. Differing from 

 D. aprinum in having 8 instead of 10 ribs, with broad flat surfaces 

 between. (Sowb.). 



Length 77, greatest diam. 7 mill, (from orig. fig.). 



Length 48, greatest diam. 3*6 mill. 



Java, Malacca (Sowb.); Torres Strait, Cape York, 3-11 fms.; 

 Wednesday Island, 8 fms. ; and west of Cape York, south of New 

 Guinea, 28 fms. (Challenger). 



D. javanum SOWB., Thes. Conch., iii, p. 102, pi. 223, f. 12 (1860). 

 REEVE, Conch. Icon., xviii, pi. 3, f. 14, (1872). WATSON, Chal- 

 lenger Scaph., p. 12. 



Watson remarks that D. octogonum, which this very much re- 

 sembles, has much stronger intercostal striae and the ribs are much 

 more sharply prominent. It may be added that in octogonum the 

 calibre increases more rapidly, and the shell is more curved. The 

 aperture of D. javanum is as wide as long, and distinctly octagonal. 

 The single specimen we have seen is nearly white. 



D. LETSON^: Sharp & Pilsbry, n. sp. PI. 1, fig. 13 ; pi. 5, figs. 66, 



67, 68. 



Shell long and slender, the length about 12 times greatest diam- 

 eter, solid, but rather thin, well and equally curved ; pale green, 

 with numerous indistinctly defined darker zones. Sculpture, 17 

 longitudinal riblets at the apex, increasing to about 25 at aperture, 

 rather unequal in size and strength, but not conspicuously so, the 

 smaller ones being intercalated irregularly ; all the main riblets 



