MOLLUSCA OF THE ' CHALLENGER ' EXPEDITION. 443 



flatly rounded at the tip. Whorls 10, short, angulated, but. only 

 by the prominence of the tubercles, which also gives the ap- 

 pearance of a sutural contraction ; the last is small, with a 

 rounded, very abruptly contracted, conical base, prolonged 

 into a small prominent snout, which is almost imperceptibly 

 bent backward. Suture linear, but well marked from the profile- 

 lines of the whorls above and below meeting at a slight angle. 

 Mouth pear-shaped, angulated above, and a little produced 

 below. Outer lip very regularly curved, but straight along the 

 canal, a little contracted in the middle : on leaving the body it 

 does not immediately bend to the left, thus leaving a narrow but 

 well-marked shelf along the whole upper edge of the rather 

 deep, narrow, rounded sinus, below which it advances into a high- 

 shouldered pinion : it scarcely retreats below this till close to the 

 point of the snout. Inner lip is very narrow ; it is scarcely 

 convex on the body, and is somewhat angular at the base of the 

 conical pillar, down which it runs with a somewhat thickened, re- 

 verted, and prominent edge defined by a small furrow; it is 

 scarcely cut off obliquely in front with a narrow, thickened, 

 rounded edge. H. 0*46. B. 016. Penultimate whorl, height 

 0-07. Mouth, height 0*18, breadth 0-07. 



This species a good deal resembles P. micans, Hds. ; but is a 

 much narrower form, with a higher and finer spire, more numerous 

 whorls, and is not merely tubercled, but has its tubercles pro- 

 longed into ribs. Than P. pudiea, Hds., it is longer, narrower, 

 with a deeper suture, a shorter canal, and a much blunter apex. 

 P. sigmoidea, Bronn, is broader, the whorls are longer, the apex is 

 blunter, the body-whorl is much longer, and that species has no 

 open constriction below the suture. 



42. Pletjeotoma (Thesbia) ebitima, n. sp. (Ipm/tos, very 

 precious.) 



St. 135. October 18, 1873. Nightingale Island, Tristao da 

 Cunha. 100-150 fms. Bock, shells * 



Shell. — Very small, but hardly thin, oblong, spirally striated, 

 with a long body-whorl, a rather high conical spire, a blunt 

 round-pointed apex, and a short broad truncated snout. Sculp- 

 ture. Longitudinals — there are exceedingly faint scratches in the 

 * I have copied for this set of dredgings the note appended to the box which 

 contained them. In the list of stations there is nothing which exactly answers, 

 though in the hook of stations issued for the naturalists its place is recog- 

 nizable. 



