392 KEY. B. BOOG WATSON ON THE 



tion are 5 or 6 pretty prominent, unequal, narrow, remote, rounded 

 threads ; the one which comes out from the suture at the upper 

 angle of the mouth, and which defines the base, is somewhat 

 stronger than those above it, and this one is succeeded on the base 

 by a series of others, similar, but more remote, with occasionally a 

 finer one between ; on the base they become feebler, less regular, 

 and, on the whole, more remote ; the surface of the shell between 

 these is faintly scored microscopically. Colour porcellanous 

 white and semitransparent, from the thinness of the shell. Epi- 

 dermis an excessively thin, pale-yellow, smooth membrane, which 

 is very easily rubbed off. Spire high and conical, and yet almost 

 globose from the rapid increase of the rounded whorls ; its profile- 

 lines are much interrupted by the sutural contractions. Apex 

 consists of 1 J embryonic whorls, and is small, rounded, mamillary, 

 prominent, but a little flattened down on one side. Whorls 6, of 

 very rapid increase, the last particularly so ; they are very tumid 

 and well rounded, with only a slight angulation, above which 

 is a long convex shoulder, while below it the whorl contracts 

 very slightly ; the last is very large, being not only tumid, but 

 having an elongated base which, though considerably hollowed out 

 on the left side, is very little narrowed on the right, and is pro- 

 duced into a long, conical, largish snout, which projects almost 

 entirely on the right side of the axis. Suture rather broad and 

 deeply sunken, and almost a little canaliculated. Mouth long, 

 large, club-shaped, being oval and bluntly pointed above, and 

 having a long, rather narrow, and open canal below. Outer lip 

 very sharp and thin, a little contracted except along the canal, 

 where it is slightly \ patulous ; the curve of the lip, which is 

 very ; steep above, passes over, by a slightly flattened arch and 

 a concave curve below, to a straight line along the canal ; 

 its edge, on leaving the body, retreats rather rapidly to the 

 left, forming the deep semicircular sinus which occupies the 

 whole shoulder from the suture to the angulation ; the lower 

 edge of the sinus is very low-shouldered, but advances very 

 prominently below, and retreats no more till it reaches the 

 extreme point of the shell. Inner lip is hollowed rather broadly 

 out of the shell-wall, the edge of which rises sharply, but very 

 thinly, outside ; it spreads across the whole of the rather short 

 and early truncated pillar, which has a long, oblique, rounded, 

 and slightly twisted edge, and which above joins the body with 

 a very slightly concave curve. Operculum pale yellow, thin, oval, 



