no 



Genus 8. PLEUROTOMA, LamarcL 



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, hut 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 loith the body 

 li^horl, with a sinus or deep fissure. Operculum horny, acumi- 

 nated at the lower end. 



The genus Pleiirotoma includes a very extensive group of mollusks, 

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

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

 analogous to the sUt in Siliquaria, the sinus in Emarginula, the foramen 

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

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

 closely allied to Fnsus and other Canalifera, in wliich no indication of this 

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

 in Conm 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 wliich it is allied to the proximate genera. 



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

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

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

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

 paratively deep water. 



Species. 



1. abbreviata, Reeve. 5. seruginosa, id. 9. albicans (C'/a«.)> Hinds. 



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



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



4. aegi-ota, iP^eye. 8. albibalteata, zW^, 12. albina, i«»i. 



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



