CLAUSILIA. 



275 



cannot be the case, because in these mollusks 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 

 fur Malakozoologie ' for June 1847, p. 84. 



Genus IX. CLAUSI'LIA*, Draparnaud. 

 PL 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, 

 pear-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 columella, as well as with a flexuous plate or fold be- 

 hind the pillar lip and curved plates or folds within the outer 

 lip ; besides these various processes there is a peculiar and 

 complicated apparatus 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 flattened ram's-horn, serving the purpose of an 

 operculum : outer lip continuous and forming a complete 

 peristome : basal crest (which is formed by an upward and 

 abrupt twist and contraction of the last whorl) more or less 



* Furnished with a dausilium or operculum -like process. 



