no 



Genus 8. PLEUROTOMA, Lamarck. 



Animal ; " disc short, oval, thin at the margin, at the posterior 

 extremity of which is placed a rather thick horny operculum, 

 similar in most respects to that of Buccinum, and conse- 

 quently not spiral, but terminating behind in a sharp point ; 

 head flattened, and from the angles protude two conical 

 pointed tentacles at the base and outer side of which are two 

 eyes ; mantle similar to that of Fusus, excepting that it has 

 an incision at the side corresponding to the slit in the shell."* 



Shell; turreted, fusiform, spire acuminated; columella smooth, 

 ending in a canal, which is sometimes straight and elongated, 

 sometimes short and a little recurved ; aperture small, lip 

 simple, emarginated at or below its junction with the body 

 whorl, with a sinus or deep fissure. Operculum homy, acumi- 

 nated at the lower end. 



The genus Pleurotoma includes a very extensive group of mollusks, 

 mostly small, in which the mantle is slit at the side in such a manner as to 

 impart a corresponding character to the sheD, and which may be said to be 

 analogous to the slit in Siliquarla, the sinus in Emarginula, the foramen 

 in Haliotis, &c. It is scarcely necessary to observe that the animal of 

 Pleurotoma has no affinity with these genera, but is, on the other hand, 

 closely allied to Fusus and other Canalifera, in which no indication of this 

 character is to be found. The incision in the mantle, which occurs also 

 in Conus and in some species of Melania, does not therefore seem to be a 

 character of so much generic importance in Pleurotoma, as the turreted 

 fusiform growth of the shell, by which it is allied to the proximate genera. 



The shells of Pleurotoma, like those of Turbmella, have the canal some- 

 times straight and elongated, sometimes short and recurved, and the species 

 exhibit great variety of sculpture. They are very numerous, widely dis- 

 tributed both in the eastern and western hemispheres, and dwell in com- 

 paratively deep water. 



Species. 



1. abbreviata, Reeve. 5. aeruginosa, id. 9. albicans (Clav.), Hinds. 



2. abyssicola, Forbes. 6. affinis, Gray. 10. albicostata, Soto. 



3. iEgeensis, id. 7. alabaster, Reeve. 11. albifuniculata, Reeve. 



4. segrota, Reeve. 8. albibalteata, id. 12. albina, Lam. 



* Deshayes, Anim. sans vert. vol. ix. p. 344. 



