3312 



THE MOLLUSKS OR SHELLFISH 



marine forms, and are deposited separately. They are mostly round or egg shaped, 

 and are generally laid in the earth under stones or leaves, and there left to hatch 

 by themselves. On emerging from the egg, the animals are practically the same as 

 the parent, but the form of the shell, when present, generally alters very much in 

 the course of growth. 



SHELLED SLUGS Family TESTACELLID^E 



The shelled slugs or Testacellidce have no jaws, but are armed with a tongue 

 bearing oblique series of long, narrow, pointed teeth, indicative of their carnivorous 

 habits. While some members of the family are without any external shell, the 

 majority are provided with shells capable of entirely covering the animals, but a 

 few have only very small ear-shaped shells attached to the upper surface of the 

 hinder end of the foot. To the latter group belongs Testacella, the typical form of 

 the family. This genus includes elongated slug-like animals, with the breathing 

 orifice at the posterior end of the body, which is capable of great extension and con- 

 traction. They prey upon earthworms, which are pursued in their burrows under 

 ground. In a recent account of the habits of T. scutulum, Mr. Webb observes that 



it usually seized the anterior 

 end of the worm, and gradu- 

 ally swallowed it; but occa- 

 sionally the middle was 

 seized, in which case the 

 worm forced itself away. 

 During cold northerly and 

 easterly winds these crea- 

 tures inclose their bodies in 

 a kind of cocoon, like that 

 of the silkworms, which is 

 secreted from the skin, and 

 often mixed with earthy and 

 extraneous particles. These 



slugs deposit a few calcareous eggs, which in form are as symmetrical as those of a 

 bird, and large in proportion to the size of the animal. It is doubtful whether this 

 genus is truly indigenous to Great Britain, or merely an introduction of compara- 

 tively modern times. The only other parts of the world besides Europe where 

 Testacella occurs, are Algeria and the Azores, Madeira, and Canary islands. 



Glandina forms an extensive genus of Testacellidce, chiefly restricted to the 

 central parts of America; one species, however, being European. Like Testacella, 

 these are very voracious, and even attack their own species. Daudebardia is another 

 slug-like gen us of this family, carrying a small shell upon the tail. They occur in 

 Southern and Eastern Europe and Western Asia, and in New Zealand are closely 

 represented by Schizoglossa, the external aspect of which is very similar. The 

 allied Streptaxis is remarkable for the peculiar obliquity of the last or body whorl 



SHELL-BEARING SLUG, Testacella haliotidea. 

 (Natural size.) 



