320 REV. R. B00& WATSON OIT THE 



contraction, wMle tLe outer expands a very little, as is the case 

 in TJtriculus uonbilicatus, Mont. ; at tlie upper end is a small, 

 narrow, but deepisb rounded sinus. Outer lip : its edge is 

 very straight, retreating a little quickly above and slightly in 

 front; its direction is straight, with the very slight bend to 

 the right spoken of above. Tojo a little contracted, rounded, 

 with a sort of thickened pellucid disk* which is almost perfectly 

 horizontal, so that the whole top of the body-whorl and the 

 upper corner of the mouth are on the same level : in the centre 

 is a minute closed pore. Inner lip : there is a thin narrow glaze 

 which thickens and expands in front : it is not expanded on the 

 top. Pillar is short, slightly oblique and twisted, with a strongish 

 defined tooth, in front of which it is rather abruptly truncate. 

 L. 0-156. B. 0066. Mouth at same place, B. 0-014. 



C. ])roiracta, Grould, is very like this in front, but rises much 

 higher above. G. cylinclracea, Pennant, is slightly slimmer or nar- 

 rower in proportion to length, has the body-whorl a little smaller, 

 and the mouth slightly broader, lacks the slightposterior narrowing, 

 and is squarely truncate behind, while here the shell is rounded. 

 The ' Challenger ' species, too, quite wants the very peculiar form of 

 the ujoper corner of the mouth which is characteristic of O. cylin- 

 dracea. G. discus differs from G. inacra, Wats., in being a little 

 broader, and having a totally different top of shell and mouth. 

 G. alha, Brown, of the same size, is rounder and less cylindrical, 

 being more attenuated above especially ; the mouth is extended 

 above the top of the shell ; the top of the body- whorl is more 

 oblique and less truncated. 



2. Ctlichna tahitensis, n. sp. 



Sept. 28, 1875. Tahiti harbour, near the reefs, 20 fms. 



Shell. — Cylindrical, thin, glassy, spirally sti'iate from end to 

 end, with a small body, rounded outlines, no depression nor central 

 point at the apex, and a toothless but abruptly truncated and 

 prominent-pointed pillar. Sculpture. Longitudinals — there are 

 scarcely perceptible lines of growth. Spirals — the whole surface 

 is covered with fine grooves not quite regular, about -g^o in. 

 apart, but weaker and more crowded in the middle than at 

 either extremity. Golour bluish transparent glossy white. Mouth 

 rather large and long. Outer lip has a sinus just above the body, 



* Hence its name. 



