o4 AKT. 2. — 5^. TOXUXAOA. 



side, rounded in cross-section ; the lengtli about ten to eleven 

 times the diameter of the aperture. Longitudinal ribs promi- 

 nent near the apex, gradually decreasing in size towards the 

 posterior, so that they are obsolete on the anterior third of the 

 shell. At apex there me eight to eleven rather sharp and well 

 raised ribs, separated by wider concave intervals ; at a short 

 distance from the apex, an interstitial riblet appears in these 

 intervals, so that the ribs and the riblets alternate each other ; 

 in larger specimens there is a still smaller thread between the rib 

 and the riblet. Circular sculpture not conspicuously developed. 

 Apex with a v-shapcd notch at the convex side. Length 55-80"™. 



On consulting the descriptions and figures given by Duxker 

 and PiLSBRY, this species is closely allied to Dentalium [Antalis) 

 weinkauffi Dkr., but in fossil specimens the ribbed portion is 

 not so distinctly separated from the smooth portion as shown in 

 the figure of the living specimens. Moreover, the number of 

 ribs at the apex is greater in the living than in the fossil one. 

 One fragmentary living specimen collected in Asamiwan, pro- 

 vince of Tsushima, and another one said to have been collected 

 at an unknown place in Japan probably belong to the same 

 species. 'J1ie question whether the fossil form is really identical 

 with Dental'mni iveinTcauffi Dkr. can only be settled by compar- 

 ing a still greater number of specimens both living and fossil. 

 The fossil has been taken by Brauxs for Dentalium entale Li.nné. 



Shinagaw^a (abundant). 



90. BENTALTIM EDOENSTS Tor. 

 PI. II. Fit-. 17. 



Shell smidl, curved, very slender and tapering, thin and 

 fragile, slightly swollen close to the aperture ; surface glossary, 



