MOLLUSCA. 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, 
er 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 Linneeus, constitute a very natural 
family, which may be termed Purap, distinguished by the 
mouth being, in general, furnished with teeth, or testaceous 
lamina, 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 Virrmva.—Margin of the shield doubie. 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 rounded. 
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 Draparnaud and named Suc- 
crngA. Afterwards Lamark proposed the term Amphibu- 
lina, but latterly adopted that of Draparnaud. Thename first 
employed indicates one of the most striking characters of the — 
