MOLLUSCA OF THE ' CHALLENGER ' EXPEDITIOjS". 511 



Animal. — Mantle is white, very thin, and transparent ; the ad- 

 ductor muscles are short and weak. The liver is small, of a 

 light greyish brown. The mouth of the mantle is very strong, 

 of a yellowish colour, and the animal is rather fawn-coloured. 



Shell. — Like one of the old drinking-horns, short, stumpy, and a 

 good deal bent, rather thin ; the newer growth porcellanous, the 

 older chalky, and given to break off in flakes, leaving a perfectly 

 smooth brilliant porcellanous core. Sculpture. The surface is 

 covered with close-set annular strise, which, especially on the 

 longitudinal ribs, show like minute, crisp, round threads. The 

 longitudinal ribs are very much stronger, but still are fine, 

 rounded, parted by rounded furrows much like the ribs ; both, 

 but especially the farrows, are irregular in size, fresh riblets 

 arising in the hollows. There are from 30 to 35 toward the 

 apex, and from 70 to 80 toward the mouth. Colour pure white. 

 Edge thin and broken at the mouth ; at the apex there is an ir- 

 regular ragged fissure in the convex curve. L. 1*8 in. B. at 

 mouth 0'3, at apex 0"07. 



One specimen from St. 246 is much less curved than the others. 

 That from St. 299 (distant 4500 m. N. and S., and 6000 m. E. 

 and W.) is much broader (L. 1'7, B. 0"36) and much more bent, 

 but is obviously identical. 



This, compared with D. anipliialum, W., is more curved ; the 

 loDgitudinai strise are much narrower, more distinct, and more 

 persistent. Than D. grande, Desh., this is a much smaller and 

 especially shorter and stumpier form, without the regular circular 

 lirse, and the longitudinal ribs are much weaker and are closer 

 set. Compared with D. capillosum, Jeffr., which it superficially 

 resembles, it differs in texture, form, and sculpture. 



5. DeNTALIUM DIAERH05, W. {Ziappiol.) 



St. 169. July 10, 1874. Lat. 37" 34' S., long. 179° 22' E. N.E. 



from New Zealand. 700 fms. G-rey ooze. 4 specimens. 



Animal. — Mantle white, body pale yellow. Captacula many, fine, 

 long and equal, with small ovoid points. Foot and collar those 

 of a true Dentalium. 



Shell. — White (chalky), but porcellanous beneath the surface ; 

 rather straight, with a considerable bend near the apex, of rather 

 rapid expansion from a very fine apex. Sculptiore. The whole 

 surface is faintly marked with scarcely impressed longitudinal 

 lines of very equal interval (about 0*0055 apart) ; transversely 



