TURBID^. 



Gasteropodous dioicous operculate testaceous 

 aquatic mollusca, having a single pair of ten- 

 tacles, with the eyes situated externally upon 

 an enlargement of the base: shell spiral, more 

 or less globose or subdiscoidal, with the aper- 

 ture entire. 



The great and somewhat heterogeneous 

 family Turbida^ nearly corresponds to the genus 

 Turbo, Lin.; to Blainville's second family Cri- 

 costomata, of his second order Asiphonobran- 

 chiata; and to Cuvier's family of Trochoides 

 (which includes the Melaniana) of his sixth 

 order Pectinibranchiata. It includes, according 

 to each of these systems, genera which, like 

 Helicina, appear to belong more properly to the 

 pneumonobranchiate section. 



Mr. J. E. Gray makes the genera Ampullaria, 

 Paludina, and Valvata, the types of as many* 

 distinct families. These genera are indeed very 

 distinct, but whether they should be considered 



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