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CYCLADID.E. 



A GROUP of freshwater mollusks, whose shells resemble 

 those of Kellia or of Astarte, but whose soft parts present 

 structures conspicuously distinguishing them from the tribes 

 to which either of those genera belongs. The shells are 

 more or less tumid, equilateral or inequilateral, thin, as in 

 our British forms, or thick, as in the foreign Cyren(E^ smooth 

 or concentrically striated and furrowed, and covered with 

 an epidermis. The hinge is furnished with cardinal and 

 lateral teeth, and the ligament is external. The animals 

 have plain-edged mantles, open in front ; siphonal tubes 

 produced, and either partially separated or completely 

 united to their unfringed extremities ; and a large lingui- 

 form foot. They live buried in the mud of slow streams, 

 lakes, ponds, ditches, and springs. Our native species are 

 all ovoviviparous. They breed readily in confinement, and 

 often exhibit considerable activity, ascending the sides of 

 the vessel in which they are placed. 



CYCLAS. Bruguiere. 



Shell equivalve, thin, suborbicular, more or less inflated, 

 slightly inequilateral, closed, smooth or concentrically 

 striated. Cardinal teeth minute (in British species), one in 

 the right and two in the left valve ; lateral teeth developed. 

 Ligament external, more or less conspicuous, placed on the 



