20 PALUDINID^. 



raised longitudinal wrinkles, and the last whorl or two 

 are occasionally encircled with a few almost obsolete 

 ridges. There are five peculiarly rounded volutions, whose 

 increase, from a small, but very blunt apex, is moderate 

 as to height, but rapid as to breadth. They are short, 

 since the usual breadth of the penult is nearly thrice its 

 Avidth, and are divided by a suture, that from the ab- 

 rupt rise of the turn above it, and a slight horizontal 

 compression in that below it, appears profoundly dis- 

 tinct. The spire, which, viewed from above, is of about 

 the same length as the body, is obtuse. The base of 

 the shell is somewhat compressed horizontally, but still 

 is more or less convex. The umbilicus is abrupt, and 

 though not capacious, is tolerably large. The laterally 

 projecting aperture is continuous, circular, disposed to 

 expand, occupies fully one half of the basal diameter, 

 and is about equal in length to the spire. The outer 

 lip is acute, simple, and slightly recedes in front ; it 

 forms no angle with the erect pillar-lip, which latter 

 curls back a little, yet is not reflected. From the ob- 

 liquity of the last whorl, it lies, at the mouth, entirely 

 or" nearly below the preceding one, instead of clasping 

 it, so that the front extremity of the aperture projects 

 below the general level of the base. The coils of the 

 niultispiral operculum enlarge quickly near the margin. 

 The diameter of the shell is very nearly a quarter of an 

 inch. 



The animal (which was first noticed by Montagu) is of a 

 pale grey colour with setaceous tentacula, eyed at their exter- 

 nal bases, and bears a tentacle-like appendage near the head 

 on the right side. Its pellucid delicate retractile branchial 

 plume projects from over its neck. " Between the months 

 of May and August,'' wiitcs M. Bouchard Chantereaux, 



