CYCLOSTOMA. 185 



stones and fallen branches, as well as among moss 

 and dead leaves. 



This tiny but very beautiful mollusc is timid and 

 inactive ; when crawling its shell is carried horizon- 

 tally. Its slime is abundant and watery. It delights 

 in moist situations, and Moquin-Tandon says that it 

 can remain submerged for a considerable time without 

 injury. 



In winter it may frequently be found in the hollow 

 stems of aquatic and other plants. 



SECTION III. 

 FAMILY V.-CYCLOSTOMATID-ffi. 



Body spiral, capable of being entirely contained within the 

 shell ; mantle covering the front part, its margin separate from 

 the neck, at the back of which the pulmonary cavity is situated ; 

 snout long ; tentacles 2, contractile ; eyes situated at the outer 

 base of the tentacles ; foot elongated. 



Shell spiral, conical or cylindrical ; mouth round or oval ; 

 operculum testaceous, or horny, paucispiral ; lingual ribbo7i 

 narrow, with large teeth, three on each side of the central one. 

 The sexes are distinct. 



In Great Britain this family is represented by two 

 genera, each containing a single species only. 



GENUS I.—CYCLOS'TOMA* DRAPARNAUD. 



Body oblong ; tentacles cylindrical, tips slightly tumid ; foot 

 rather broad. 



Shell conical, usually solid ; whorls rapidly enlarging ; mouth 

 circular ; operculum testaceous, strong, spire nearly central. 



* Circular mouth. 



