DENTALIUM. 23 



the apical contraction, reminding one somewhat of D. sectum, cala- 

 mus, etc. We have seen no specimens. 



D. iNTERCALATUM Gould. PI. 11, figs. 88, 89. 



Shell strongly curved and conspicuously tapering in its earlier 

 half, the later half nearly straight and less tapering ; white, luster- 

 less. At and near the apex hexagonal in section, the angles rather 

 sharp and a little projecting, intervals nearly flat. Not far from 

 the apex a secondary rihlet arises in each of the two faces on the outer 

 curve, and somewhat later the lateral faces and those on the concave 

 side are similarly divided ; the secondary riblets gaining rapidly in 

 strength, and on the latter part of the shell equal to the six primary 

 ribs. Toward the aperture there are 12 equal, equidistant ribs, 

 rounded but well projecting, and about half as wide as the concave, 

 excavated intervals, which are smooth except for light growth strise. 

 Aperture circular, the outer edge of peristome scalloped by the ribs. 

 Apical orifice circular, about half as wide as the truncated apex. 

 Length 19, diam. at aperture 2-25, at apex 0*9 mill. 



China Seas (North Pacif. Expl. Exped.). 



D. intercalatum Gould, Proc. Bost. Soc. N. H., vii, p. 166 (1859) ; 

 Otia, p. 119. — SowERBY in Conch Icon., xviii, pi. 7, f. 45 (1872). 



In D. hexagonum the secondary riblets when developed do not 

 arise so soon, and the six primary angles are stronger. Figure and 

 description from the type in U. S. National Museum, No. 24183. 



Sowerby's figure copied on plate 6, fig. 85, is not characteristic, 

 from its much greater proportionate diameter, 



D. PSEUDOSExAGONUM Deshayes. PI. 4, figs. 47, 48. 



Shell cylindrical, subulate, somewhat curved, grayish-white, some- 

 what transparent. At the apex there are 6 strongly projecting 

 equidistant angles ; between each of these ribs a great many strise 

 arise, covering the shell, and the primary ribs rapidly decrease and 

 disappear at the first fourth or third of the shell's length. Growth 

 strife quite fine and often regular. Length 45-50, greatest diame- 

 ter 4 mill, (from Desh.). 



Masbate, Philippines; TF. Colombia (Sowb.); Cape York, near 

 Albany I., N. Australia, 11 fms. ; Darnley I., Torres Straits, 30 fms. 

 (Chevert Exp.), 



D. pseudosexagonum Desh., Monogr. Dent., Mem. Soc. Hist. Nat. 

 Paris, ii, p. 358, pi. 16, f 14, 15, 16 (1825).— Sows., Thes, Conch., 



