DENTALIUM. 33 



Singapore (Sowerby, S. Archer) ; Samar, Philippines (Sowb.) ; 

 China Sea (A. N. S. P.) ; Darnley 2., Torres Straits, 30 fms. (Chev- 

 ert Exp.). 



D. dispar Sows., Thes. Conch., iii, p. 103, pi. 224, f. 37 (1860); 

 and in Conch. Icon., xviii, pi. 4, f. 25 (1872). BRAZIER, Proc. 

 Linn. Soc. N. S. Wales, ii, p. 58 (1877). 



Young shells taper more rapidly, as usual, and of course a greater 

 part of their length is sculptured. The summits of the four primary 

 ribs are subdivided by one or two longitudinal grooves in this spe- 

 cies, but are simple in D. quadrapicale and D. quadrangulare. 



D. QUADRICOSTATUM Brazier. 



Shell white, very slightly arched, four angled, keel or rib at each 

 angle, rounded, finely serrated, interstices flat, marked with trans- 

 verse lines ; apex perforated, perforation entire ; aperture angled. 

 Length, 8 lines ; diam. of base, 1 line [16, 2 mill.]. (Brazier). 



Princess Charlotte Bay, north-east Australia, 13 fathoms; York 

 Island, Torres Straits, 13 fathoms, hard mud ; Katow, New Guinea, 

 8 fathoms, sandy mud. (Chevert Exped.). 



D. quadricostatum BRAZ., P. L. S., N. S. W., ii, p. 58 (1877). 



If this species is laid upon its side it forms a true square; when 

 resting with the arched part of the apex down, it forms four angles, 

 with a serrated rib on each angle. The 11 specimens from Katow, 

 16 from Princess Charlotte Bay, and 1 from York Island, all have 

 the same character. (Brazier). 



D. DIPSYCHA Pilsbry & Sharp, n. sp. PI. 4, figs. 57, 58, 59, 60. 



Shell slender, the length about 11 times the diam., well curved, 

 attenuated toward the apex ; white, nearly lusterless. Sculpture : 

 at and near the apex square in section, with four acute, narrow, pro- 

 jecting, longitudinal, pinched-up ribs, the spaces between flat ; not 

 far from the apex in each face a median thread arises, and soon 

 equals the primary four in size ; each interval then bears a tertiary 

 thread, and here the section of the tube has become circular. At 

 about the middle of the length another set of interstitial threads ap- 

 pear ; so that at the aperture there are 32 flat, equal, low, but abruptly 

 defined riblets separated by flat interstices of about the same or 

 slightly greater width. Interstices everywhere plain except for cir- 

 cular growth-lines, which are moderately obvious throughout. 

 3 



