34 DENTALIUM. 



Aperture rounded, somewhat compressed antero-posteriorly, the 

 inner margin less curved; hardly oblique; peristome thin. Anal 

 orifice circular, occupying a very short tube. No slit. Length 45, 

 antero-posterior diam. of aperture 3*8, lateral diam. 4'1 mill. 



Habitat unknown. 



This species differs from D. dispar in the simple primary ribs, 

 lack of fine, even longitudinal striation, and persistance of the 

 sculpture to the aperture. D. quadrapicale is allied, but has a much 

 more oblique aperture, more rapidly tapering tube, and though far 

 smaller, a greater number of much finer longitudinal riblets. 



D. QUADRAPICALE ' Hanley ' Sowerby. PL 4, fig. 50. 



Shell rather stout, apical third strongly curved, the remainder but 

 slightly arcuate ; white, shining. Sculpture, four angles at the apex 

 (giving that part an almost square section, the two outer sides of the 

 square slightly longer), situated at the outer, inner and lateral sur- 

 faces, the faces between them straight and flat ; these angles rapidly 

 lose in prominence, and the intervals become convex ; very near the 

 apex each interval becomes parted by a secondary riblet ; and the 

 interstices between these are again divided by tertiary threads at 

 about the end of the first third of the shells length ; and subdivision 

 proceeds until at the aperture there are about 36 low, subequal rib- 

 lets, with narrow, shallow intervals, and the tube is subcircular, a little 

 flattened antero-posteriorly, in section. Growth-striae faint. Aperture 

 very oblique. Anal orifice without slit or notch. 



Length 20, length of aperture, measured obliquely 3, breadth 3 

 mill. 



Length 31*5 mill (original figure). 



Cochin ; Malabar (Hanley coll.). 



D. quadrapicale Hanley MS., SOWERBY, Thes. Conch., iii, p. 103, 

 pi. 225, f. 61 (1860) ; and in Conch. Icon., pi. 7, f. 46. D. quadri- 

 picale CLESSIN, Conch. Cab., p. 13. 



The square apex and rounded, oblique aperture are strong points 

 of difference from most known species. Sowerby's figure shows the 

 anal orifice minute and round ; but in the single specimen we have 

 seen it is large and square, the shell walls thin. 



D. TESSERAGONUM Sowerby. PI. 4, fig. 51. 



Shell moderately arcuate, tapering, attenuated toward the apex, 

 rather thin, white. At the apex square, with four equal faces, the 



