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



body, across which, with an oblique course, it runs nearly straight, not truncating the 

 pillar, but narrowing it to a point. H. 0-098 in. B. 0'034. Mouth, height, outside 

 0-031, inside 0-028 ; breadth, outside 0'029, inside 0*019. 



This is a remarkably elegant species, with, none of the contortion of the genus ; it has more of 

 the aspect of a Scalaria than any of its congeners. 



8. Rissoina triangularis, 1 n. sp. (PI. XLVJ. fig. 7). 



September 8, 1874. Flinders Passage, near Cape York. 7 fathoms. 



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

 Island, Cape York, North-east Australia. 8 fathoms. Coral mud. 



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

 North-east Australia. 6 fathoms. Coral mud. 



Shell. — Narrow, long, square in front, white, ribbed and spiralled, with a high spire, 

 a small rounded top, convex whorls, an impressed suture, a contracted base, a very long 

 pillar, a varixed triangular mouth, and very peculiar outer lip. Sculpture : Longitudinals 

 — there are on each whorl 12 or 13 rather narrow, little raised, rounded, oblique, widely 

 parted ribs, which are feeble at the suture, and die out on the base ; they are parted by 

 wide shallow furrows of from three to four times their breadth. Spirals — the whole sur- 

 face is scored with fine rounded threads, parted by shallow furrows of about three times 

 their breadth, and also by very minute superficial spiral scratches, which give a frosted 

 look to the shell. Colour white, with a slight tinge of ochre. Spire high and narrow, 

 conical, with scarcely convex profile-lines. Apex is small, but ends rather abruptly in a 

 flatly tabulated top, on which the extreme rounded tip just rises into view ; the first three 

 whorls are embryonic, and are quite smooth. Whorls 8, convex, short, and narrow, only 

 the last being of any size, and it but small, having a very contracted rounded base. 

 Suture rather strongly contracted, and very horizontal. Mouth large, having almost the 

 shape of a right-angled triangle, the whole inner lip forming the hypotenuse, and the 

 right angle lying at the outer corner of the base. Outer lip runs forward very straight 

 from its insertion to the outer corner of the base, where it turns nearly at a right angle, 

 and runs almost straight across to the point of the pillar ; its two parts are nearly equal : 

 this straight long line across the front of the shell is a very peculiar feature ; the sinus at 

 either end of the lip is small and shallow, but that at the front of the pillar is extremely 

 angular ; the sharp but strong front edge is very sinuous, and on the base especially is 

 very prominent ; the external varix is narrow, but well marked. Inner lip carried 

 straight by a thin pad from the insertion of the outer lip to the point of the pillar, which, 

 though insignificant in the mouth, projects long and straight from the base. H. 0*15 in. 

 B. 0-055. Mouth, height 0-048, breadth 0'038. 



1 So called from the shape of the mouth. 



