250 LIMNiEIDiE. 



in the same manner as Pedijjes by alternately fixing and 

 moving forwards the anterior locomotive disk. 



Species of Otina. 

 fusca, A. Adams. otis, Flem. 



Fam. LIMNiEID^E. 



Lingual membrane armed with numerous quadrate teeth, 

 arranged in transverse rows, the central minute, the laterals 

 uncinated. Head with a broad, short muzzle dilated at the 

 end ; mouth with a horny upper mandible ; tentacles flat- 

 tened or filiform, with the eyes sessile at their inner bases. 

 Mantle-margin variously modified ; respiratory orifice at the 

 right side. Foot flattened, lanceolate or ovate. Excretory 

 orifices on the left side of the neck. 



Shell of varied form, thin, horn- coloured, usually with 

 an oblique fold on the columella, and with the outer lip 

 simple and acute. 



Animal fluviatile, living in the water, but coming to the 

 surface to respire the free air. 



The fresh-water, air-breathing Mollusks of which this 

 family is composed inhabit the rivers, ponds, and running 

 streams in all parts of the globe, being, however, most 

 numerously represented in temperate regions. They are 

 entirely phytophagous in their habits, feeding on Con- 

 fervas and other aquatic plants. Although usually to be 

 seen crawling on the muddy bottoms and on the stems and 

 foliage of submerged vegetables, they always come to the 

 surface to respire the free air, and sometimes may be ob- 

 served gliding, shell downwards, on the surface of the water, 

 anchoring or letting themselves down occasionally by means 



