68 



/. 1. et 91 1,-/.. 2. No fossil shells appear to have been found, which 

 can be referred to this genus. 



XXXIV. Pleurotoma. A fusiform, or somewhat turreted univalve, 

 with the lower part of the opening channeled, and the upper part of the 

 lip notched. 



The shells of this genus had been separated from the .murices; and, 

 on account of their form, had been disposed by Bruguiere in the genus 

 Fusus. But the notch in the lip, resulting, necessarily, from a peculiar- 

 organization in the animal, fully authorizes their arrangement in a dis- 

 tinct genus. This separation of Pleurotoma from Fusus, as is justly 

 observed by Lamarck, appears, indeed, to be indicated by the con- 

 siderable number of species which each of these genera contains. Of 

 this genus only, he obtained twenty-five species from the neighbourhood 

 of Paris : PL fiiosa, P. lineolata, P. davicularis, P. glabrata, P. marginata, 

 P. transversaria, P. catenata, P. dentata, P. undata, P. tmdtinoda, P. crcnu- 

 lata, P. bicatenata, P. costellata, P. plicata, P. sulcata, P. curvicosta, P. fur- 

 cata, P. nodulosa, P. ventricosa, P. terebralis, P. granulata, P. in/leva, 

 P. twrella, P. striarella, et P. decussata, 



Plate V. Fig. 26, represents a beautiful species of this genus, from 

 France. 



