192 INTRODUCTION TO CONCHOLOGY. 



reception of a newly- discovered mollusk^ allied to the 

 common slug, but, instead of liaving a shell inserted near 

 the neck, it is situated about the middle of the back, and 

 is enclosed in a small fleshy scutellum, or shield. 



Limaces, or garden-slugs, a genus of mollusks with 

 which most people are familiar, appear to have been men- 

 tioned in the earliest records of natural history, but the 

 knowledge of their being occasionally provided with an 

 internal shell is comparatively of modern date. They have 

 few, if any, redeeming qualities in the opinion of gardeners, 

 and yet even these unsightly creatures have a place in the 

 creation, for which they are wonderfully constructed. They 

 possess an internal shell, as already noticed, which is in- 

 serted within a fleshy shield upon the back of the neck, 

 and may be described as somewhat irregular, nearly square, 

 smooth, and of a calcareo -crystalline composition, with a 

 thin epidermis. 



Another variation, with regard to the position of the 

 breathing cavity, occurs in the genus Testacellus. This im- 

 portant organ is placed far back, and consequently the 

 shell, which in this genus is uniformly external, is fixed, 

 as it were, to the tail. 



The Vitrina somewhat resembles his brother Testacellus j 



