HELICID.E. 401 



haliotidea (Fig. 192), which is provided with a very small shell placed 

 at its posterior extremity, just over the pulmonary cavity. This shell 

 becomes more important in 

 Vitrina, already spoken of as 

 forming the point of transition 



between Liniax and Helix. Fig>m Testacella haliotidea (Draparnaud) . 

 This passage from Limaceans 



entirely destitute of shells to those furnished with a very small shell, 

 as in Testacella, is very exactly indicated by Nature. Limax rufus, 

 spoken of above, presents, under the posterior part of the cuirass, calca- 

 reous, unequal, isolated granulations, which are, so to speak, the 

 elements, as yet internal, of a shell which is on the point of being 

 built. Other species in the same genus present under the cuirass a 

 little rough, imperfect scale, which seems to be produced by a great 

 number of these calcareous granulations, which show themselves in an 

 isolated state in Limax rufus. 



The Helicidae is the fifth family we shall now consider. 



It is only necessary to witness the snail as it creeps along the 

 gravel walks of a garden, or in the damp alleys of a park, in order to 

 see that it is a being of higher organization than the headless molluscs. 

 The common snail (Helix aspersa) goes and comes ; it roams and 

 saunters after its own peculiar manner, searching for its food or its 

 pleasure ; it has a head and two prominent tentacles, which feel and 

 seem to express their sensations ; it has nerves", a brain, a strong 

 mouth, and a well-formed stomach. 



Without possessing a high order of intelligence, the snail is by no 

 means imbecile ; it knows very well how to choose a tree the fruit of 

 which is agreeable to it. A fine cluster of grapes, a succulent pear, 

 which the horticulturist devours with his looks, and hopes to devour 

 otherwise, is sure to be the identical fruit which will be chosen by our 

 enlightened depredator, the snail. 



The body of the snail is oval, elongated, convex above, flat below. 

 The convex or upper surface of the body is rugged, in consequence 

 of the existence of numerous tubercles projecting slightly, and sepa- 

 rated by irregular furrows ; its anterior is terminated by an obtuse 

 head, its posterior more flat and less pointed. All the flat portion, 

 thick, soft, and upon which the animal moves itself by a creeping 

 motion, bears the name of the foot. The head is not really very 



2 D 



