is in some instances furnished with teeth, and almost 

 always joined by a fiini Ugament. Such shells which 

 attach themselves to rocks, pieces of wood, or to other 

 shells, adhere by a thread-like substance, called a heard. 

 The umbilicus in a shell is a hollow which is more or 

 less wide and deep, in the centre of most univalve shells. 

 The operculum is a shell-like substance attached to 

 several of the mollusca family, which, w'len the animal 

 is within, completely closes the entrance (of the shell) 

 and thus shields it from danger. A convolution is a 

 whorl or coil, and the number of convolutions are the 

 number of coils or circles rolled upon each other, the 

 exterior whorl being the largest, and the innermost one 

 ending in a point. The epidermis is the outer covering 

 which gives lustre to the shell. The carina is the keel 

 or edge of the shell ; and the aperture is the opening . 

 The general terras arc in this manner briefly explained . 



The eyes of mollusca are placed in the horns of the 

 animal. Molluscous animals are generated in two 

 modes, one branch depositing membraneous eggs, 

 whilst another group are ovo-viviporous, that is, bring 

 forth their young alive, and in shells. In this latter 

 manner does Paludina-vivipora produce its offspring. 

 T have examined this shell microscopically. Having 

 obtained some females, and destroyed tbem by placing 

 them in hot water, from ten to a score shells (or young 

 ones) were extracted from each, in various stages of 

 perfection ; besides these there were about half-a-dozen 

 milky-white egg-shaped substances, in some of which 

 the form of the shell was, at the spiral end, plainly 

 delected. 



Parasitical insects are found on the bodies of mol- 

 lusca, and worms in their intestines. 



Molluscous animals vary considerably in the period 

 at which they arrive at maturity. Most Helices begin 

 to breed before they have attained their ordinary 



