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



Mouth sub-oval, a little oblique to the axis, bluntly pointed above. Outer lip patulous, 

 with a thin-edged, remotely varixed lip ; its sweep is a very regular curve, and its front 

 line level. Inner lip not thick, but distinct on the body ; on the pillar it is narrow, sharp, 

 and prominent, with a minute umbilical channel behind it. H. 0*075 in. B. 0"04. Mouth, 

 height 0-031, breadth 0-028. 



This species much resembles Rissoa punctura (Mont.), in sculpture, but the longitudinals are 

 straighter and stronger, the apex is blunt and flat, and the last whorl is smaller. 



In this last respect it is more like Rissoa jeffreysi, Waller, but in sculpture it is less like that 

 species, and the mouth is smaller. 



Than Rissoa abyssicola, Forbes, this is a smaller, narrower, thinner shell, with stronger sculpture, 

 a more oblong and superiorly pointed mouth, and a sharper tip. 



18. Rissoa (Alvania) trajectus, 1 n. sp. (PL XLIV. fig. 6). 



September 7, 1874. Torres Strait, Cape York, North-east Australia. 3 to 11 fathoms. 



September 8,1874. Flinders Passage, near Cape York, North-east Australia. 7 fathoms. 



Station 186. September 8, 1874. Lat. 10° 30' S., long. 142° 18' E. Wednesday 

 Island, Cape York. 8 fathoms. Coral mud. 



Station 187. September 9, 1874. Lat. 10° 36' S., long. 141° 55' E. Near Cape 

 York. 6 fathoms. Coral mud. 



Station 188. September 10, 1874. Lat. 9° 59' S., long. 139° 42' E. West of Cape 

 York, off south-west point of Papua. 28 fathoms. Green mud. 



Shell. — Small, strong, conic-obovate, reticulated, white, with a tumid body-whorl, a broad 

 round base, short spire, few conical whorls, an excavated suture, and a short pear-shaped 

 mouth. Sculpture : Longitudinals — there are on the last whorl about 1 8 narrow, well-raised, 

 rounded, slightly oblique ribs, which stop abruptly at the periphery, not being present in 

 the sutural channel, nor almost at all on the base ; they are crowded on the earlier whorls, 

 but on the body- whorl the flat furrows which part them are wider than the ribs ; the last 

 rib broadens into a strong labral varix. Spirals — above the periphery there are six 

 distinct crowded rounded threads, which score the ribs ; below the last of these there is a 

 little furrow, which forms the contraction for the suture ; below this on the base are 

 about five rounded slightly parted threads. Colour white. Spire short, and stumpily 

 conical, subscalar. Apex small, rounded, ending in the minute dome-shaped tip, which 

 just rises into view in the middle ; the first two whorls are microscopically striated 

 spirally. Whorls 5 in all, short and broad, with a barely convex conical outline ; the 

 last is round and tumid, with a faintly concave conical base. Suture nearly horizontal ; 

 it is itself indistinguishable at the bottom of a little narrow deep rounded nick-like trench. 



1 With a reference to Flinders' Passage, the place of its finding. 



