162 INTRODUCTION TO CONCHOLOGY. 



Eoman camp are yet visible on the summit of a hill which 

 rises above the cave, a fact that seems to throw some light 

 as regards the date of the bleached skeleton that lay there. 

 Whatever might have been the occupation of the spirit 

 that once inhabited it, the vicinity of a camp would afford a 

 motive for residence in a spot which is now a wind-beaten 

 and uninviting soHtude. 



Pamily XI. Peristomata. 



Worthless, percliance, men call them ; yet, methinks. 



Sages might gather ^N-isdom, on marsh sides. 



Or where lone waters, dark and sullen, creep, 



'Mid ferns and sedges ; for most strange forms dwell 



Within their precincts, creatures that can breathe 



In air or water, as the seasons change 



From wet to dry. 



Shell globose or somewhat turreted, and covered with 

 a dark olivaceous epidermis ; aperture generally round, 

 with the margin continuous. Animal fiuviatile, furnished 

 with an operculum, either horny or calcareous. 



Three genera are referred to this family. The first, 

 Vali-at(^-, are generally found upon aquatic plants, or in 

 ponds and ditches. They may readily be recognized by 



