PLLMONATA. 65 



Body convex, rounded, quite free nearly to the respirator}' 

 aperture, and lying on a flat ])laee on the back of the foot, with 

 a keeled edge on the margin of the hinder ])art. Back of the 

 neck with three grooves, the central one double, the lateral bent 

 down to the hinder part of the side of the head. Orifice of 

 generation at the hinder base of the right tentacle. Respiratory 

 aperture in the middle of the mantle shield ; mantle with a large 

 central hole, exposing part of the shell. Foot slender, com- 

 pressed, keeled at the upper edge, truncated behind ; subcaudal 

 gland distinct, ])eiijendicular. Teeth numerous, in very close 

 crowded cross lines, comjjressed, with a flat ridge ending in two 

 teeth. 



3. Par.macellus punctatus. — Va)i Hasselt, Bull. Sci. Nat. 



1824, iii. 82. 

 Hab. Java. 



4. Parmacellus t^niatus. — Van Hasselt, Bull. Sci. Nat. 



1824, iii. 82. 

 Hab. Java. 



5. Parmacellus reticulatus. — Van Hasselt, Bull. Sci. 



Nat. 1824, iii. 82. 



Hab. Java ; higher regions. 



These three species are not described. M. Van Hasselt ob- 

 serves, that they all have a slit in the envelope which covers the 

 shell : this sht is usually closed, but the animal can at will open 

 it so widely as almost entirely to expose the shell. 



*** Shell exposed, more or less covered by the thicJcened edge 

 of the collar of the mantle, or by fleshy processes of the 

 mantle which are expanded over it. 



8. VITRINELLA. 



Shell imperforate and veiy slightly perforated; spire conic; 

 whorls rapidly enlarging, last large, rounded or keeled. Peri- 

 stome simple, not reflexed. 



Animal : the hinder pait of the mantle produced and more or 

 less covering the hinder j)art of the })enultimate whorl. Foot 

 truncated behind, subcaudal gland linear. 



Vitrina, sp., Quay df Guimard, Voy. Astrol. ii. 136. 

 Nauiua, sp.. Beck, Index; Pfeiffer, Mouog. 



