LIMACID^. 



The land-slugs are elongated, semi-cylindrical, soft, or 

 fleshy creatures, either unfurnished with shells, or provided 

 with the rudiments of them, imhedded in the cloak, or 

 disk, which covers the anterior portion of the hody. This 

 disk covers the respiratory cavity, the orifice of which, and 

 the vent, are seen at its right margin. The generative 

 orifices vary in difl:erent groups. All the slugs have a 

 retractile head, four tentacles, also retractile, the two upper 

 ones provided with eyes. Their skin secretes abundant 

 mucus. They are herbivorous by preference, but carni- 

 vorous when taste or necessity prompts them. They are 

 crepuscular or nocturnal in their habits. 



The dentition of the Limacidce^ and of all our native 

 Pulmomfera, has been made the subject of elaborate in- 

 vestigation, by Mr. William Thomson, of King"'s College, 

 London. The general results of his researches are given 

 in a very excellent memoir, read before the British Asso- 

 ciation in 1850, and published in the seventh volume 

 of the second series of the Annals of Natural History. 

 They would appear to influence very importantly, our con- 

 clusions respecting the disposition and affinities of the 

 pulmoniferous genera. The edge teeth in this family have 

 a long projecting single apex. 



