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



the whorls are more rounded, the apex is not conical, but subscalar, and there are minute spiral 

 threads 0-0025 in. apart, of which there are none in any of the specimens of this species. It should 

 be noticed that the presence, partial presence, or absence of the epidermis affects considerably the 

 aspect of this shell. 1 



39. Rissoa (Setia) principis, n. sp. (PI. XLIV. fig. 13). 



Station 145. December 27, 1873. Lat. 46° 43' S., long. 38° 4' 30" E. Between 

 Marion Island and Prince Edward Island. 140 fathoms. Volcanic sand. 



January 9, 1874. Lat. 49° 8' S., long. 70° 12' E. Koyal Sound, Kerguelen. 

 Shore. 



Shell. — Moderately strong, oval, bluntly conical, white, smooth, with a large blunt 

 rounded tip, convex whorls, an impressed suture, a broad rounded base, an unvarixed lip, 

 and a large round mouth. Sculpture : the only lines are those of growth, which are hair- 

 like and close. Colour white, more or less translucent, under a thin membranaceous 

 yellow caducous epidermis. Spire conical; but the profile-lines are much interrupted. 

 Apex broad and bluntly rounded. Whorls 5, well rounded, of rather rapid but regular 

 increase. Suture deeply impressed, scarcely oblique. Mouth large, roundly oval. Outer 

 Up sharp, patulous all round. Inner lip flat and thin on the body, slightly curved, 

 patulous and sharp on the pillar, with an umbilical furrow, but no chink behind it. 

 H. 0-083 in. B. 0'051. Mouth, height 0-038, breadth 0-031. 



This is a larger and broader form than Rissoa marionensis. 



40. Rissoa (Setia) australis, n. sp. (PI. XLV. fig. 1). 



January 9, 1874. Lat. 49° 8' S., long. 70° 12' E. Eoyal Sound, Kerguelen. 

 Shore. 



Shell. — Thin, ovate, conical, pale horny, smooth, with a blunt rounded tip, slightly 

 convex whorls, a very slightly impressed suture, a slightly produced rounded base, an 

 unvarixed lip, and a smallish oval mouth. Sculpture : except fine lines of growth, there 

 is none. Colour pale translucent horny, under a thin yellowish epidermis. Spire coni- 

 cal. Apex bluntly roundedly conical. Whorls 5, with convexly conical sides ; the last is 

 long compared with the others. Suture slightly impressed, rather oblique. Mouth 

 smallish, oval. Outer Up sharp, unvarixed, a little contracted, except on the base. Inner 

 Up continuously curved, adherent right across the body, sharp and very slightly patulous 

 on the pillar, with a minute furrow, but no chink behind it. Operculum oval, subspiral, 

 thin, membranaceous. H. 0'075 in. B. 0-044. Mouth, height 0-031, breadth 0'027. 



