31 



curvature, and disposition of the ribs. It is narrower, lonjrer. less curved, constantly of a 

 yellowish-white uniform color, without transverse zones. The ribs, numbering 8, g or lo, are 

 contiguous at their bases, moderately raised and rounded. They are more elevated toward the 

 apex, diminishing gradually and disappearing toward the aperture. They are interrupted by 

 sorae growth lines. The aperture is small relative to the length of the shell. 

 Length 50, diam. 4 mill. (P. & Sii. from Desh.). 



Distribution. New Guinea (Lesson). 



R e m a r k s ; Pluricostatiiin and Lessoni resemble each other in many points. Pbiricos- 

 tatuiii is distinguished by being more slender and having secondary riblets while the transverse 

 sculpture is more pronounced than in Lessoni. The possibiHty exists that a greater series of 

 specimens may prove that the forms intergrade. 



Group of D. SHOPLANni Jousseaume. 

 14 — 21 ribs at and near apex. 



K e y t o species. 



I. Shell cylindric or nearly so. 



a. 14 — 19 longitudinal strongly granose ribs: length 55 mill. about 



7 — 8 times the greatest diameter transver sostriattint. 



a'. 17 — 21 subequal narrow ribs, increasing to 25; conspicuously 

 transversely striated; length 78 mill. about 7 — 8 times the 

 greatest diam shoplandi. 



a" . 16 narrow rounded ribs at apex increasing to about 40. Trans- 

 verse structure inconspicuous. Length 45 about 7 — 8 times the 



greatest diam malayanuni. 



II. Shell slightly dorso-ventrally compressed ; 16 ribs at and near apex, 

 secondary .sculpture mainly or arising earlier on the concave curve. 



a. Sculpture becoming anteriorly subobsolete. Length 35 — 45 mill., 



II — 10 times the greatest diam sedecimcostattun. 



a' . Ribs increasing to 48 at the anterior aperture. Length 35, diam. 



of apert. 2,8 mill compressiuscuhim. 



a" . Ribs cancellated. Length 40 — 60 mill., 9 — 10 times the greatest diam. inartensi. 



a" . Ribs simple, the interstices conspicuously transversely striated. 



Length 51 mill. about 12 — 13 times the greatest diam. . . clathratum. 



*32. Dentaliuin s /top /a Jtdz ]oussea.ume. PI. I, fig. 12. 



1894. Dcntalintii slioplandi Jouss. Buil. Soc. Philomath. de Paris, (8), VI, p. 102. 

 1897. Dentaliuin shophvuli Jouss. PiLSBRY & Sharp, Man. of Conchology, vol. XVII, p. 28, 

 pi. 12, fig. 100. 



