REPOET ON THE GASTEROPODA. 77 



I described this in my Preliminary Report (loe. cit. supra) as Trochus Icacnsis, after careful com- 

 parison of the Challenger shell with the British Museum specimens of Trochus zonatus (Wood), 

 believing that there were points of difference sufficient to separate it from these. I have since had 

 an oppoz-tnnity of examining a very large series of specimens brought by a friend from the Cape, 

 and I am satisfied that the Challenger shell belongs to Wood's species. 



43. Trochus [Margarita) brychius, 1 Watson (PI. V. fig. 7). 



Trochus (Margarita) brychius, Watson, Prelim. Report, pt. 4, Journ. Linn. Soe. Lond., vol. xiv. p. 699. 



Station 152. February 11, 1874. Lat. 60° 52' S., long. 80° 20' E. About 900 miles 

 S.E. of Kerguelen. 12G0 fathoms. Diatom ooze. 



Shell. — Globosely depressed, with 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 puckerirjgs, with stronger folds 

 about O'OOo in. broad and 0*005 in. apart. These folds tend on the last whorl to dis- 

 appear, 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 

 penidtimate 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, which, toward the mouth, especially when wet, is faintly shot 

 with a green and pink iridescence. Spire 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 apex is round and blunt, and terminates abruptly, but all the earlier whorls 

 have lost their outer layer. Whorls 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 carried across the short junction with the body by a thin nacreous callus, 

 which is continued within, and is, in fact, the completion of the whorl into a tube. Inner 

 lip slightly thickened, curved, just barely reflected. Umbilicus wide and pervious, 

 exposing all the whorls, and strongly cross-hatched within by the spiral and longitudinal 

 threads. Operculum very thin, clear, and bright, with about eight faintly-defined turns, 

 and marked with microscopic concentric lines. H. 0"64 in. B. 0'87, least - 62. Penulti- 

 mate whorl, 0-18. Mouth, height 0'43, breadth 0*4. 



This shell slightly recalls Helix cricetorum, Mull., but much more closely resembles some of the 

 West Indian land-operculates, such as Aulopomd. With its semi-continuous peristome it very much 



1 /3pu^/o5, the deep sea. 



