19 



Length 78 mill., dorso-ventral diameter 6 mill.: transverse diameter 5,5 mill. 

 Length 82 mill., dorso-ventral diameter 7 mill.; transverse diameter 6,5 mill. 



Sowerby's diagnosis is as foUows: Shell strongly arcuate, pale tawny or greenish, angulated 

 by 8 ribs, the interstices wide and flat; apical slit small. Differing from D. apritmtn in having 

 8 instead of 10 ribs, with broad flat surfaces between. 

 Length 77, greatest diam. 7 mill. 

 Length 48, greatest diam. 3,6 mill. 



Distr ibu t i on. Java, Malacca (SowB.); Torres Strait; Cape York 3 — 11 fms; Wednesday 

 Island, 8 fms West of Cape York, south of New Guinea, 28 fms; (Challenger). Karachi 

 (Melv. & St.). 



Remarks. The shell of D. javammi is less solid than o{ D. octangulatuin. It is more 

 slender, longer and the ribs are narrovver and more raised than in octangulaUun. 



Dcntalümt filostmi Broderip & Sowerby (1830 — 32, Zool. Journ. V, p. 48) is probably 

 an extinct name for what may have been D. javaimm. Here follows the diagnosis: 



"Shell slender, thin, white; with 8 longitudinal threads, and very close transverse striae. 

 Leno-th 65, diam. 5 mill. Tenasserim on shore. Distinguished from D. ocfogonuin 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 Hav, who himself picked them up on the coast of Tenasserim". 



This insufficiënt description without figure makes it impossible to identify the form with 

 certaint)-. The type is not in the British Museum. 



17. Dentalium tubiforiuc n. sp. PI. VI, fig. 5. 



Stat. 159. o°59'.iS., 129° 48.8 E. 411 Metres. Coarse sand. i Spec. 



Stat. 212. 5°54'.5S., 120° 19'. 2 E. 462 Metres. Fine grey and green mud. i Spec. 



Diagnosis. Shell well curved, tapering in the young individual, but in the older specimen 

 keeping nearly the same diameter over the longest part of the .shell. Eight-ribbed, the ribs 

 sharply cut at the top, anteriorly rounded, but ver)^ narrow, standing out like marginating rods. 

 Beautifully transversely striated the striae cancellating the ribs, so that it can be feit by rubbing 

 one's nail over the ribs. Interspaces deeply concave at the top, flat toward the anterior 

 aperture, with some inconspicuous longitudinal threads, giving together with the transverse striae 

 a reticulated appearance to the .shell's .surface (seen under a lens). In both specimens obtained 

 by the Siboga, the apex is broken in rather a peculiar way. Over a small distance the ventral 

 wall has disappeared and only the thick-walled dorsal side remains visible. Probably the apex in 

 perfect specimens is simple, with a thickened dorsal wall and a very thin ventral wall. Peristome 

 octagonal, the sides flat, the angles faintly raised. 



a. Length 45 mill., greatest diam. 3 mill. 



b. Length 25 mill., greatest diam. 2 mill. (young). 



Colour white or with a dark brown deposit at the anterior end. 



