ECTOPHTHALMA. 273 



in humid situations, as the Cyclophoridce ; while others 

 again are found near the shore within the influence of the 

 tide, as Truncatella and Paludinella, or in marshy places, 

 as Assiminia ; the three latter genera seem to resemble in 

 many essential particulars the family Littorinidce. 



Sub-order ECTOPHTHALMA. 



Eyes on the side of the head at the outer bases of the 

 tentacles. Foot rather elongate. 



Operculum horny or shelly, distinctly spiral, or annulated 

 and non-spiral. 



As constituted at present, this division includes but two 

 families, readily distinguished by the nature of the oper- 

 culum, which in the Cyclophorida is spiral, and in the 

 Heiicinidce is annular. 



Fam. CYCLOPHOKIDjE. 



Tongue narrow, with seven rows of recurved, hooked 

 teeth. Head proboscidiform ; tentacles subulate ; eyes on 

 the outer side of the bases of the tentacles. Foot elon- 

 gated. 



Operculum distinctly spiral, testaceous, cartilaginous or 

 horny; whorls very numerous and sub-equal, or few and 

 rapidly-increasing. 



Shell usually covered with a horny epidermis ; aperture, 

 for the most part, circular. 



The animals of this extensive family are found in the 

 humid parts of tropical forests, either concealed among the 

 debris at the roots of trees, or inhabiting the branches and 

 the foliage; they are also met with in dry and arid situa- 



