DENTALIUM-FISSIDENTALIUM. 69 



but otherwise identical. Mine was dead and surface not glossy, 

 yours living (though eroded), and in places quite glossy. If the two 

 had been dredged together 1 think no question would have arisen as 

 to their being the same. From such different localities there is 

 always more doubt, though, in these abyssal things without much 

 reason for it. Mine has no notch, but I find such differences in this 

 character in the same species that I put no value on it unless it is 

 uniform in many specimens. There do not seem to be any other 

 differences. After a most careful scrutiny, I think there are no 

 specific or even definable varietal difl^erences between them." 



" This {D. ceras) compared with Dentalium amphialum Wats, is 

 more curved ; the longitudinal strise are much narrower, more dis- 

 tinct, and more persistent. Than Dentalium grande Desh. this is 

 much smaller and especially shorter and stumpier form, without the 

 regular circular lirae, and the longitudinal ribs are much weaker 

 and are closer set. Compared with Dentalium capillosum Jeffr., 

 which it superficially resembles, it differs in texture, form and 

 sculpture ( Watson). 



The specimens from the Atlantic reported as D. ceras, we refer to 

 D. candidum var. meridionalis, young. 



D. iEGEUM Watson. ^ PI. 20, fig. 27. 



Shell long, conical, finely tapering, much and very equally bent, 

 though less, of course, as the shell grows larger ; thin, pure white, 

 porcellanous, a little chalky towards the mouth, but higher up bril- 

 liant. Sculpture : Longitudinal ridges 30 to 35, unequal, rounded 

 above, close, rather high, narrow, and parted by furrows which equal 

 the ribs, but lower down these ribs become broader and flatter, and the 

 furrows widen, till, towards the mouth, the surface becomes uniform 

 and the ridges are only indicated by the faint strise of the furrows. 

 Under a lens the whole surface shows a faint longitudinally striated 

 texture. On the upper part of the shell the strise of growth are very 

 faint, but they become rather strongly marked towards the mouth. 

 Toward the apex the outer layers for half an inch are stripped off" 

 and leave exposed the brilliant, smooth core, presenting many longi- 

 tudinal facets corresponding with the ridges of the outer layer. 

 There is an irregular short fissure with broken edges at the apex on 

 the convex curve. Length 2*5 in., breadth at mouth 0*3, at apex 

 0-33 inch ( Watson). 



Off London River, Kerguelen Island, in 110 fms. (Challenger). 



