3i8 Records of the Indian Museum. [Voi,. XIII. 



direction up to the margin of the terminal zone of accretions when 

 they finally become retrocurrent. 



The somewhat small aperture is lanceolar, posteriorly termina- 

 ted by a narrow channel, while anteriorly it contracts gradually 

 into the rather short oblique canal. The junction of the colu- 

 mella with the base of the last spire-whorl is curved though rather 

 abrupt. Anteriorly to the base of the last spire-whorl the course 

 of the columella is, on an average, straight as far as the com- 

 mencement of the canal, and slightly oblique, the direction being 

 anteriorly towards the left of the shell. Not far from the base of 

 the last spire-whorl it exhibits a blunt, broad revolving swelling, 

 clearly visible when the outer lip is incomplete. At the com- 

 mencement of the canal the columella becomes more strongly 

 oblique, but it extends anteriorly only for a very short distance as 

 a distinctly differentiated structure, the anterior portion of the 

 canal being formed merely by the thin shell-wall without any 

 differentiated columellar margin or columella. The columellar 

 margin is almost everywhere very thin : it has a very slightly raised 

 edge at the commencement of the canal, posteriorly to which it is 

 quite flush with the adjoining outer surface, except at its posterior 

 termination where it exhibits a small button-like callous thickening 

 resembling that of a Drillia, which contributes to contract the 

 posterior channelled termination of the aperture. The outer lip 

 which is very thin terminates normally to the suture. The sinus 

 is moderately broad, very deep without any raised edge. The 

 convexity of the outer lip, anteriorly to the sinus, does not 

 project much further forward than its posterior termination, The 

 internal walls of the shell are hrate, but the internal Hrae cease at 

 a considerable distance from the aperture. 



In the two specimens in which the outer lip is complete, or 

 almost complete, it exhibits a most peculiar structure which does 

 not appear to have been noticed or described in any other Pleuro- 

 tomid shell. The two anterior main threads of the convexity of 

 the base, on approaching the aperture, grow into extremely promi- 

 nent trumpet-like hollow expansions which, nevertheless, do not 

 breach the margin of the outer lip whose outline is continuous, the 

 hollow expansions being, in the present condition of the shells, 

 quite shut off from the interior of the shell. It is evident, how- 

 ever, that this was not so at the time of their formation, and that 

 they must have originated from a more or less siphon-like fold of 

 the mantle with the formation of a deep sinus which was afterwards 

 obliterated. This peculiar growth was evidently several times re- 

 peated, for there are several of these trumpet-shaped foliaceous ex- 

 pansions fitting inside one another, the last ones becoming gradu- 

 ally smaller on approaching the present aperture. It is more- 

 over to be noticed that the growths are not simultaneous on the 

 two main threads which are affected by them. On one of the 

 specimens, it is upon the most anterior of the main threads of the 

 convexity of the base that this structure is first observed ; then, 

 without any closing of the temporary sinus thus produced, the 



