94 DENTALIUM-GRAPTACME. 



D. novae hollandice CHENLT, 111. Conch., i, p. 5, pi. 6, f. 14. 

 Like so many of Chenu's species, this is known by the original 

 publication only. It is unusually large for the present group. 



D. ACUTISSIMUM Watson. PI. 20, fig. 26. 



Shell long and much attenuated, rather straight and very regu- 

 larly curved, very thin, brilliant and glassy. Sculpture: The sur- 

 face is crossed by fine, sharpish, irregular striae, which run very 

 elliptically round. In the young shell the surface is regularly and 

 finely scratched by a great number of close-set, regular, sharp and 

 extremely minute lines, which very gradually become more and 

 more faint, but are still traceable even in the full-grown shell. The 

 color is pure white, transparent, and almost hyaline in the fresh 

 shell, but in the dead shell the interior (not, as usual, the exterior) 

 layers of the shell become opaque and chalky. The edge is very 

 thin and irregularly broken. At the apex the end is abruptly 

 broken off in one specimen, and in the other there is an irregular 

 fissure with an internal lining process. In one specimen from Sta- 

 tion 246, which is full-grown, but very short, a large, thin, irregu- 

 larly shaped process projects, which, being obliquely cut off some- 

 what across the shell, supplies the anal orifice. Length 1'52 in., of 

 young specimens from Station 218 ; breadth at mouth 0*12, at apex 

 0-026 inch. Length 1-14, of old and broken specimen, Station 246 ; 

 breadth at mouth 0'23, at apex 014 inch (Watson). 



N. of Papua, 1070 fms.; mid- Pacific, E. of Japan, 2050 fms. 

 (Challenger). 



D. acutissimum WATS., Journ. Linn. Soc. Lond., xiv, p. 514 ; 

 Chall.Rep.,p.8,pl. l,f.8. 



Compared with Dentalium leptoskeles Wats, this is more curved, 

 more conical, and thus not nearly so attenuated. Compared with 

 Dentalium agile Sars also, this is more curved, rather more conical, 

 and very much more delicate. It is likewise, when full-grown, ap- 

 parently larger than either. Than Dentalium lubricatum G. B. 

 Sow. this broadens more rapidly, is more brilliant, the circular 

 striae are stronger, the longitudinal are finer, closer and sharper. It 

 is also straighter than that species. Than Dentalium pretiosum Nut- 

 tall this broadens faster and is much more brilliant. Dentalium 

 perlongum Dall lacks the faint longitudinal striae, is much straighter 

 and is more slender ; thus if one chooses a point where the breadth 

 in the two species is equal, then within about an inch Dentalium 



