12 



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 rather wide and rounded, generally wider than the intervals; 

 the concave side as a whole with stronger sculpture than the convex side; growth striae faint. 

 Aperture slightly compressed laterally, not oblique. Anal orifice shortly ovate, the narrower end 

 toward the convex side; no slit or notch. Length 75, length of aperture 6, breadth 5,5 mill.; 

 diam. of apex 2 mill.; height of arch from chord 13 mill. 



Distribution. Island of Bohol, Philippines. 



Remarks. ^Messrs Pilsbry & Sh.\rp add.: "With the color and general shape of D. 

 aprinum, this species presents less prominent and many more longitudinal riblets, without trace 

 of the definite arrangement seen in that species. It is not especially related to aprimim except 

 being of a green color. The aperture is noteciably compressed from side to side. The figures 

 on pi. 5 [(PI. I, fig. 5)] represent the sculpture at the apex and aperture, with an outline of 

 the latter". 



Compare D. inicrsiriaiimi. 



Group of D. HEXAGONUM. 



He.xagonal or si.x-ribbed at and near the apex. 



I. The whole shell decidedly hexagonal. 



a. Intervals smooth or only with a few striae .... hexagomini, sexcostatiim, inimts. 

 a . Intervals finely ribbed intercostatum. 



II. .Shell he.xagonal only at the top. 



a. With secondary riblets, all ribs persistent toward aperture. 



Length ± 45, greatest diam. 4 mill pseudosexagoniDii. 



Length zL 20, greatest diam. 2,5 mill porcatiiin. 



Leng-th ± 22, o-reatest diam. 2 mill duodecimcostaUim. 



a . A few secondary riblets, all ribs vanishing toward aperture, niichelottii. 



*6. Dentalium hexagomtm Gould. PI. I, fig. 14. PI. VI, fig. i. 



1859. Dentaliitni hexagonuin Gould, Proc. Bost. Soc. N. H. VII. 



? Dentalium liexagomnn Gould, Otia Conch. 

 i860. Dcntaliinn hexagonuin Gould. SowERBV, Thes. Conch. III. 

 1872. Dentalium hexagonuin Gould, Conch. Icon. 



1874. Dentalium hexagotium Gould. LiSCHKE, Jap. Meeres Conch III. 

 1897. Dentalium hexagoniim Gould. PiLSBRY & SHARP, Manual of Conchology, vol. XVII, 



p. 18, pi. 2, figs 20, 21 and var. 23, 24. 

 Not Dentalium hexagonum Sowerby. 



Diagnosis. Shell white, solid, well-curved, hexagonal (by exception heptagonal) in 



