CLAUSILIA. 275 



cannot be the case, because in these moUusks each indi- 

 vidual is both male and female. 



The shell of this species differs from the young of 

 Clausilia rugosa (which it somewhat resembles in form) 

 in being thinner and of a much lighter colour, in the 

 whorls being much more convex, and especially in the 

 periphery or basal edge being rounded, instead of sharply 

 angular as in the young shell of that species. 



It is the Pupa fragilis of Draparnaud ; and Moquin- 

 Tandon has retained it in that genus. The Balia Sarsii 

 of Philippi appears to be only a variety of the present 

 species, judging from his description in the ^ Zeitschrift 

 fiir Malakozoologie ^ for June 1847, p. 84. 



Genus IX. CLAUSI'LIA^, Draparnaud. 

 PI. VII. f. 12, 13, 14. 



Body long and slender, always containable within the shell : 

 tentacles 4 ; upper pair rather long and prominent ; lower pair 

 very short and resembling conical nipples : foot long and 

 narrow. 



Shell sinistral, spindle-shaped, rather solid, usually ribbed 

 transversely, and always more strongly, or wrinkled, towards the 

 mouth : spire reversed, long and pointed : mouth small, j)ear- 

 shaped, and twisted on the body whorl, having a deep sinus or 

 groove at its upper angle, furnished with two spiral plates and 

 sometimes also with intermediate ridges or teeth on the colu- 

 mella, as well as with a flexuous plate or fold behind the pillar 

 lip and curved plates or folds within the outer lip ; besides 

 these various processes there is a pecuhar and complicated ap- 

 paratus lying deep within the throat or cavity of the mouth 

 and consisting of a moveable and elastic nacreous -white plate 

 or ossicle, which is twisted and somewhat resembles a flat- 

 tened ram's-horn, serving the purpose of an operculum : outer 

 Up continuous and forming a complete peristome : hasal crest 

 (which is formed by an upward and abrupt twist and contrac- 

 tion of the last whorl) more or less prominent : umhilicus verj 



* Furnished with a clausilium or operculum-like process. 



