PLANAXIDiE. 321 



whorls few, smooth ; aperture large, ovate, entire, peristome 

 continuous ; inner lip callous ; outer lip simple ; umbi- 

 licus rimate. 



Syn. Lithoclyptus, Christ, and Jans. Paludestrina, 

 D'Orh. Lithogiypter, Fitz. 



Ex. L. lapidum, i>'0/-J/^/??/, pi. 34, fig. 1. Operculum, 

 L. naticoides, Ferussac, fig. 1, «, 1, b. Shell, L. nati- 

 coides, fig. 1, c. 



The typical species of this genus is from the river Da- 

 nube ; a few other species are inhabitants of the fresh 

 waters of South America, and have been described by 

 M. D'Orbigny under the name of Paludestrina. 



Species of Lkhoglyphus. 



fuscus, Ziegl. piscium, DVrb, 



lapidum, D'Orh. prasinus, Koch. 



naticoides, Feruss. 



Fara. PLANAXIDJE. 



Lingual membrane with seven series of teeth (3'1'3), 

 the outer lateral teeth conical, curved. Rostrum elongate; 

 tentacles subulate, with the eyes sessile at their external 

 bases. Mantle with a produced siphon in front ; gill in 

 several lines on the inner side of the mantle-cavity. Foot 

 simple, or furnished with tentacular filaments. 



Operculum ovate, subspiral. 



Shell with the fore part of the aperture emarginate. 



Marine. 



In general structure, as well as in their habits, the ani- 

 mals of this family most nearly resemble the Liitori- 



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