DENTALIUM-L^VIDENTALIUM. 103 



II. Shell with slight or moderate curvature, 

 a. Aperture circular or nearly so. 



b. Apex slit on the concave side ; bluish-white, polished ; 

 length 24-27 mill., 12-13 times the diameter. West 

 Indies, alloschismum, p. 108. 



b r . Apex notched on both convex and concave sides. 



c. Moderately curved ; yellow corneous ; length 



33 mill., 11 times the diam., bmnuatum, p. 108. 



c'. Nearly straight ; reddish toward apex ; length 



55 mill., about 14 times the diam. ; Australia, 



erectum, p. 111. 

 b." No notch on concave side. 



c. Shell white, with annular swellings ; Mediter- 

 ranean, siculum, p. 107. 

 c'. No annular swellings. 



d. Very slender; length 50-80 mill., about 

 25 times the diam., perlongum, p. 104. 

 d'. Less slender ; salmon or carnelian tinted 

 toward apex. 



e. Length 41 mill., about 15 times the 

 diam. ; Antillean, matara, p. 105. 

 e'. Length 33 mill., about 9-10 times 

 the diam. ; Mediterranean, etc., 



rubescens, mahani, pp. 105,107. 

 d" '. Less slender; white or whitish. 



e. Faintly striated longitudinally ; 

 length 15 mill., about 62 times the 

 diam. ; quite tapering, 



diarrhox, p. 109. 



e'. No longitudinal striation ; aperture 

 slightly compressed vertically ; 

 length 37 mill., about 12? times 

 the diam., leptosceles, p. 110. 



e". Length 64 mill., 10-11 times the 

 diam.; Australia, lubricatum, p. 110. 

 e'" . Smooth, subtranslucent, bluish- 

 white ; a slit on convex side ; length 

 25 mill., 12-13 times the diameter, 

 Antilles, liodon, p. 107. 



a'. Aperture and section of the tube oval. 



b. Large; length 105 mill., 11-12 times the diam., 



caudani, p. 104. 



