70 DENTALIUM-FISSIDENTALIUM. 



D. cegenm Watson, Journ. Linn. Soc. Lond., xiv, p. 509 (1879) ; 

 Challenger Rep., p. 2, pi. 1, f. 2. 



Than D. capillosum Jeffr. this is more conical, more curved, the 

 ridges are fewer, and the furrows between much wider and more 

 open ( Watso7i). 



D. OPACUM Sowerby. 



Shell nearly straight, attenuated at the apex, its diameter increas- 

 ing much more rapidly than in the other species; with 17 or 18 

 rather blunt longitudinal ribs, with a smaller one between each ; 

 all the ribs nearly obsolete at the wider extremity ; posterior fissure 

 short, dorsal. Length 225, diam 0-3 inch (G.B.S.). 



From South Sea ships, supposed New Zealand (G. Humphrey's 

 coll.). 



D. opacum G. B. S., Zool. Journ., iv, p. 198 (1828). 



A few specimens were preserved in Mr. G. Humphrey's collection 

 with the following label : " White striated elephant's teeth, per S. 

 Sea ships, supposed New Zealand " ( G. B. S.). 



D. ZELANDicuM Sowerby. PI. 6, fig. 81. 



Shell white, banded with pale gray and tawny ; slightly arcuate, 

 pyramidal, wide. Ribs numerous, but little elevated and unequal. 

 Apex slightly slit {Soivb.). Length 57, greatest diam. 8 mill, (from 



New Zealand (B. M.J. 



D. zelandiciim SowB., Thes. Conch., iii, p. 101, pi. 223, f. 13 

 (1860) ; Conch. Icon., xviii, pi. 2, f. 8 (1872). 



Very similar to D. rectum, but the sculpture is far less bold and 

 coarse (Soivb.). 



The length is about 7 times the diameter. D. pacificum Hutton, 

 in which the length is 8 times the diameter, and D. hutioni Kirk, 

 with the length about six times the diameter, are somewhat similar 

 ribbed species, the former perhaps identical. Z>. conic^mi Hutton, 

 of the New Zealand Pliocene, seems also to belong to this immediate 

 group. Compare also D. opacum. 



D. PACIFICUM Hutton. 



Shell solid, tapering, slightly curved, longitudinally grooved ; 

 grooves unequal, about 30 at the anterior end, but diminishing in 

 number toward the apex ; white. Length 2'4 ; breadth, anterior 

 end 0"3, posterior end 0'05 inch=60, 7*5 mill. {Hutton). 



Neiv Zealand (Hutton). 



