4 THE VOYAGE OF H.M.S. CHALLENGER. 



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 striae, 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 furrows, 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 irregular ragged fissure 

 in the convex curve. L. 1"8 in. B. at mouth - 3, at apex 0'07. 



One specimen from Station 246 is much less curved than the others. That from Station 299 

 (distant more than 7500 miles in a straight line, 4500 miles N. and S., and 6000 miles E. and W.) 

 is much broader (L. P7 in., B. - 36) and much more bent, but is obviously identical. 



The distance by sea from the Pacific, off Valparaiso, to the Gulf of Mexico, is so enormous that 

 Mr. Dall's identification of his species with this one seemed to need confirmation, and a specimen 

 was accordingly sent to him for comparison. Mr. Dall sent me a sketch of his solitary specimen 

 with the following remarks, which his sketch confirms, " Yours is older, has lost much tip, and 

 widened at the mouth ; the tip is perhaps slightly more curved. The sculpture in mine, perfectly 

 preserved, is a little more cleanly cut than in yours, 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 I 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 

 differences between them." 



This, compared with Dentalium amphialum, Wats., is more curved ; the longitudinal striae are 

 much narrower, more distinct, and more persistent. Than Dentalium grande, Desh., this is a much 

 smaller and especially shorter and stumpier form, without the regular circular lira?, and the longi- 

 tudinal ribs are much weaker and are closer set. Compared with Dentalium cajdllosum, Jeffr., 

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



5. Dentalium diarrhox, 1 Watson (PL I. fig. 5). 



Dentalium diarrhox, "Watson, Prelim. Eeport, pt. 2, Journ. Linn. Soc. Lond., vol. xiv. p. 511. 

 Station 169. July 10, 1874. Lat. 37° 34' S., long. 179° 22' E. N.E. from New 

 Zealand. 700 fathoms. Blue mud. Bottom temperature 40°. 



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

 with small ovoid points. Foot and collar those of a true Dentalium. 



1 dia^Ji^, rent asunder. 



