PROSOBRANCHIATA. 203 



Genus 26th. Pleurotoma.* Lamarck. 



Turris, 1797, Humphreys. 

 Pleurotoma, 1801, Lamarck. 

 Pleurotomartus, 1806, Burner. 

 Pleurotomus, 1810, Be Montf. 

 Turricula, 1817, Schum. (not Klein). 

 Pleurotoma, 1840, Swainson. 



— (exc. sect, a) 1847, Bellardi. 



Surcula, 1853, Adams. 

 Genot, 1757, Adanson. 

 Crassispira, 



•] 



, 1840, Swains. 

 Brachytoma, J 



Conopleura, 1844, Hinds. 



Genota, 1853, Adams. 



Sect. Drillia, 1834, Gray. 



Gen. Char. — Shell fusiform, turreted, or conoid, ribbed or concentrically striated., 

 sometimes smooth ; spire elevated : aperture oval, terminating anteriorly in a canal 

 more or less elongated ; outer lip thin, with a deep fissure or notch near the posterior 

 extremity ; columella smooth, nearly straight. Operculum pointed, nucleus apical. 



This genus, first indicated by Humphreys under the name Turris, was established 

 by Lamarck for various shells, which by Linnaeus, Chemnitz, and others, had been 

 placed with Murex, and by Brugniere with Fusus. The animal is very similar to that 

 of the Cone, and, like it, presents a strong resemblance to those of the Muricida, from 

 which it is mainly distinguished by the peculiar character of the dentition. It has a 

 small, flat head, provided with a siphon varying in length, and with cylindrical tentacles 

 wide apart, on bulgings near the bases of which the eyes are placed ; and the mouth 

 terminates in a small, fleshy proboscis. The foot is oblong, truncated at each extremity, 

 of nearly uniform width, and thin at the edge ; and the mantle has a notch or slit on the 

 right side which corresponds with, and is represented by, the sinus in the shell. The 

 function attributed to this notch is the more ready expulsion of the excretory matter, 

 but the precise way in which it is subservient to that purpose is not known- Appa- 

 rently it is intended, as Mr. Swainson asserts, for the protrusion of some particular 

 organ of the animal ; but the existence of such an organ is not noticed by MM. Quoy 

 and Gaimard in their description of the anatomy of the animal of Pleurotoma Babylonica, 

 nor has it as yet been ascertained. The lingual teeth are elongate, subulate, arranged 

 in two series ; but, as in the Cone animal, the central or rachidian teeth, usually found 

 in other families, are wanting. 



* Etym. flXevpa, the side ; and Tojui), an incision. 



