170 



Tamilj III. Cyclostomacea. 



A wider range have these. 

 Than such as haunt the waters : mountain's side 

 They climb unbidden ; ay, o'er mighty plains 

 They journey fearless, instinct-taught, to find 

 The smallest stream that, oozing, maketh damp. 

 It may be, some small space no eye discerns. 



The shell of the Cydostoriiacea varies exceedingly in 

 form, being either globose or turreted ; the aperture is 

 round or semilunar ; and the lip, ^Yhich is generally re- 

 flected, is sometimes indented near the columella with a 

 canal or fissure. The operculum, common to all, is either 

 horny or subcalcareous. 



This family is divided into four genera : — Pupi7ia, Trmi- 

 catella, CijclodomcLy and HeUcraa. 



Conchologists relate that the foot, or organ of locomotion, 

 in the Truncatella, is formed, as it were, of two parts, and 

 that he is enabled to move with considerable facility by 

 contracting the space between them into the form of a 

 hoop — hence the cognomen of '^^looping-snails,''^ which Gray 

 assigned to this genera; that, further, being partially 

 aquatic, the animal can live either under water or on land : 



