MOLLUSCA or THE ' CHALLENGER ' EXPEDITIOX. 699 



oblique, squarish, nacreous. Outer lip very thin, very slightly 

 descending and drawn in a little horizontally at its junction 

 with the body, and then well rounded in its whole sweep to the 

 point of the pillar-lip, near which it is externally creuulated 

 by the ends of the basal threads. I*iUar is short, straight, 

 slightly tubercled on its inner side, hardly toothed in front, and 

 still less augulated at its junction with the outer lip. The 

 pillar-lip is very thin, slightly excavated longitudinally, and re- 

 verted on the minute umbilicus, which it almost wholly conceals. 

 Behind it is a very narrow furrow. H. 0'27. B. 0'22, least 0'2. 

 Penultimate whorl 0-075. Mouth, breadth 0-117, height 0-125. 



In form and details of sculpture this species is extremely like 

 T. (Thalotia) elisci, Gould, from island of Capul, in the Philip- 

 pines (B.M.), but is very obviously different. 



5. Trochus (Margarita) brtchius, W. (/3pvxtos.) 



St. 152. February 11, 1874. Lat. G0° 52' S., long. 80° 20' E. 

 1300 miles S.E. of Kergueleu. 12G0 fms. Diatomaceous ooze. 

 2 specimens. 



Shell. — Grlobosely depressed, witli a small high spire, very thin, 

 rather opaque, rough, dull, and slightly iridescent. Sculpture. 

 The whole surface looks as if a rough epidermis were gathered 

 into close, minute, obliquely longitudinal puckerings, with stronger 

 folds about O'OOS in. broad and 0-005 in. apart. These folds tend 

 on the last whorl to disappear, except near the suture and toward 

 the umbilicus. They are crossed by fourteen to sixteen fine 

 round spiral threads, which at the crossing of each fold rise into 

 knots. On the upper surface of the body-whorl they become 

 very faint ; there are four on the penultimate whorl, the first 

 being remote from the upper suture, the last close to the lower 

 suture. Besides these the surface is microscopically wrinkled 

 spirally. Colour a dead slightly greyish white, w^hich, toward the 

 mouth, especially when wet, is faintly shot with a green and pink 

 iridescence. S^ire rather high, the earlier whorls being small 

 and very much twisted out so as to rise above one another by 

 almost their entire height. The a^ex is round and blunt, and 

 terminates abruptly, but all the earlier whorls are stripped of 

 their outer layer. Wliorls 5, very round, of very regular but 

 rather rapid increase. Suture deeply and sharply impressed. 

 Mouth rather oblique, round, not descending, brilliantly iridescent 

 within. Outer lip thin, turning down to meet the pillar-lip, and 



