MOLLUSC A. 155 



and tentacula, and at last the dart of the one is pushed forth 

 by its muscular bag, and directed against the body of the 

 other, into which it enters, never penetrating through the 

 integuments, and even, in many cases, falling short of its 

 mark. Whether the use of the dart is merely to stimulate, 

 or whether it is subservient to any other purpose, can scarcely 

 be said to be determined. 



The species belonging to this genus are numerous, and 

 exhibit, in the form, the markings, and the coverings of the 

 shell, numerous characters for their subdivision. 



The species which are related to the Turbo bidens per- 

 versus and muscorum of Linnaeus, constitute a very natural 

 family, which may be termed PUPAD^, distinguished by the 

 mouth being, in general, furnished with teeth, or testaceous 

 laminae, and the last whorl nearly the same as the preceding. 

 Perhaps the most convenient way of dividing them is into 

 two sections, the first including the dextral and the second 

 the sinistral shells. 



GENUS VITRLNA. Margin of the shield double. The 

 upper fold of the shield is divided into several lobes, which 

 are capable of being reflected over the surface of the shell. 

 The shell itself is not capable of containing the whole body 

 of the animal. The Helix pellucida of Miiller is the type 

 of the genus. It is a common British species, and was has- 

 tily regarded by Montagu as the fry of the Helix lucida. 



GENUS SUCCINEA. Termination of the pillar rounder!. 

 The mouth is large in proportion to the size of the shell, 

 with the outer lip thin, and the pillar attenuated. The genus 

 was first characterized by Dtaparnaud and named SUC- 

 CINEA. Afterwards Lamark proposed the term Amphibu- 

 lina, but latterly adopted that of Draparnaud. The name first 

 employed indicates one of the most striking characters of the 



