12 



zones. Sculpture, 17 longitudinal riblets at the apex, increasing to about 25 at aperture, rather 

 uneqiial 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. 



Distr ibu t ion. Lsland of Bohol, Philippines. 



Remarks. Messrs Pilsbry & Sharp add. : "With the color and general shape of D. 

 aprimim^ this species presents less prominent and man)- more longitudinal riblets, without tracé 

 of the definite arrangement seen in that species. It is not especially related to aprimitn 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. interstriaüun. 



Group of D. HEXAGONUM. 



Hexagonal or six-ribbed at and near the apex. 



I. The whole shell decidedly hexagonal. 



a. Intervals smooth or only with a few striae .... hexagomini^ scxcostatum^ iiiinus. 

 a . Intervals finely ribbed infercostaütin. 



II. Shell hexagonal only at the top. 



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



Length ± 45, greatest diam. 4 mill pseiidosexagonuni. 



Length ± 20, greatest diam. 2,5 mill porcatum. 



Leneth ±: 22, g-reatest diam. 2 mill duodecimcostatitm. 



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



*6. Dentalinm hexagomim Gould. PI. I, fig. 14. PI. VI, fig. i. 



1859. Dentalium hexagonuui Gould, Proc. Bost. Soc. N. H. VII. 

 ? Dentalinin Iiexagonuin Gould, Otia Conch. 



1860. DcntaliiiDi hexagonuiit Gould. SowERBY, Thes. Conch. III. 

 1872. Deiitaliiim hexagoniiui Gould, Conch. Icon. 



1874. Dcntalumi hexagonum Gould. LiSCHKE, Jap. Meeres Conch III. 



1897. Dentalium hexagomun Gould. PiLSBRY & Sharp, Manual of Conchology, vol. XVII, 



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

 Not Dcntaliuin licxagoniini Sowerby. 



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



