MOLLUSCA OF THE ' CHALLENGER ' EXPEDITION, 265 



increase to the last, which quite swallows up all the others. 

 Suture nearly horizontal, small, not at all impressed, but very 

 distinct, being slightly channelled, and being defined by the 

 small margin and compression of the whorl below it. Mouth 

 large but not very open, semicircular, oblique, almost right-angled 

 above,rounded below; the swell of the body-whorl is just perceptible 

 within ; its height is more than seven ninths of the whole height. 

 Outer lip very regular all the way round, it3 edge is thin. Inner 

 lip a little flexuous ; the upper corner of the mouth is filled up 

 with a thinnish but broad pad, whose edge crosses the body in a 

 slightly concave line ; below the umbilicus, which it completely 

 covers, it is contracted in on the pillar, which is thickish, 

 rounded, and towards the point levelled back. Operculum tes- 

 taceous, scored with slightish radiating lines ; the spire is mem- 

 branaceous, being left uncovered by the limy coat ; but the one 

 specimen which preserves the operculum is a young shell. 

 H. 0-9. B. 0-75. Penultimate whorl, height 0*19. Mouth, 

 height 0-73, breadtli 0*52. 



This species so closely approaches iV. affinis, Gmel. ( = iV T ". 

 clausa, Brod. and Sow.), that I have hesitated very much to sepa- 

 rate them, and have been glad to be strengthened in so doing by 

 the opinion of Prof. v. Martens and of Mr. E. A. Smith. N.far- 

 tilis is more globose, higher in the spire, longer and more pointed 

 in the base, and less obliquely transverse in its outline ; its apex 

 is larger and slightly more prominent. JV. globosa^ King, from Ma- 

 gellan, like this in form, is umbilicated and has a thin operculum, 



11. Natica apora, n. sp. (a7ropos, impervious.) 

 St. 191. Sept. 23, 1874. Lat. 5° 41' S., long. 134° 4' 31" E. 

 Off Arm Island. 800 fms. Mud. Bottom temperature 39°*5. 

 Shell. — Conically globose, pointed on the base, with a pointed 

 apex and a very slightly impressed suture ; smooth but not glossy, 

 buff-coloured, with white pillar-lip ; umbilicus quite closed. 

 Sculpture. Longitudinals — close-set, regular, hair-like lines of 

 growth, which above near the suture are gathered into radiating 

 puckers ; these are strongest on the upper whorls. Spirals — 

 there are traces of very slight furrows and obsolete lines, which 

 are somewhat stronger and more regular on the base. Colour : 

 below the ruddyish-yellow epidermis the shell is porcellanous 

 white. Epidermis thin, finely fibrous, persistent. Spire rather 

 high and conical, its outline being hardly broken by the rounding 

 of the whorls and the sinking in of the sutural lines. Apex large, 



