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



recalls a Cyclostrcma, all the more so that it is less pearly within, less nacreous and more chalky, and 

 less globosely conoidal than Margaritas usually are ; but I have no doubt that it is a Margarita. 

 Trochus {Margarita) umbilicalis, Brod. and Sow., is vaguely like, but is very obviously different : 

 the apes is not so exserted as here, the whorls are of much more rapid increase, and form a much 

 larger though lower spire ; the last whorl is proportionally much more tumid and above is more 

 flattened, the suture is much more oblique, the umbilicus is very much smaller and more covered by 

 the inner-lip, and the hard, polished, buff-coloured porcellanous outer layer of the shell (which is very 

 like that in Trochus (Margarita) expansus, Sow.) is very unlike. 



44. Trochus {Margarita) charopus, 1 Watson (PI. V. fig. 6). 



Trochus (Margarita) charopus, "Watson, Prelim. Report, pt. 4, Journ. Linn. Soc. Lond., vol xiv. p. 700. 



Station 149j. January 29, 1874. Lat. 48° 43' S., long. 69° 15' E. Kerguelen 

 Island. Off Cumberland Bay. 105 fathoms. Volcanic mud. 



Var. cceruleus, Watson (PL V. fig. 6b). 



Var. catmints, "Watson, Prelim. Report, pt. 4- Journ. Linn. Soc. Lond., vol. xiv. p. 701. 



Station 151. February 7, 1874. Lat. 52° 59' 30" S., long. 73° 33' 30" E. Off Heard 

 Island. 75 fathoms. Volcanic mud. 



Shell. — Globosely conical, like a Cyclophorus, thin, translucent, umbilicated, irides- 

 cent, banded. Sculpture : Of spiral threads there are from twenty-five to thirty-five, sharply 

 projecting, rounded, and fine on the last whorl ; of these, from three to seven are feebler 

 than the rest ; those on the base are continued within the mouth. The interstices are much 

 broader than the threads. The whole surface is also fretted by microscopic spirals and 

 stronger longitudinals, which follow the oblique lines of growth. Of the threads, six to 

 thirteen appear on the penultimate whorl ; they begin with the second whorl, and there 

 the longitudinals are rather disproportionately strong and regular. The embryonic apex 

 is faintly but coarsely tubercled. Colour yellowish white, shot on the upper side with a 

 dark iridescence ; the spirals are black, clouded, and broken with oblique longitudinal 

 streaks of white. The spire is high and scalar. The apex, porcellanous and scarcely 

 iridescent, is small, high, and mammillate, and consists of the one embryonic whorl, 

 which is a little turned up on its side. Whorls 6, of gradual and regular increase, 

 rounded, near the apex a little angulated by one of the spirals. Suture well marked, 

 angulated, but not sharply so. Mouth rather oblique, round, hardly angulated at the 

 upper corner, not in the least descending, brilliantly iridescent within and showing the 

 coloured spirals of the outside. Outer lip thin, slightly puckered at the spirals, a little 

 thickened on the base. Inner lip thickened and reflected, especially at its junction with 



i ■^asovoc, light blue. 



