2 LIMACID^E. 



contractile and retractile cylindrical tentacles, gradually 

 diminishing in diameter towards the end, and terminating 

 in a bulbous expansion ; the superior pair long, and bear- 

 ing, in the terminal bulbs, organs supposed to be eyes ; the 



w > 



inferior pair under the head, short and without eyes. 

 Orifices of the organs of respiration, generation, and 

 digestive excretion on the right side, but varying in posi- 

 tion in the genera. Hermaphrodite, but requiring the 

 union of two individuals for fecundation. Shell rudi- 

 mentary or none. Herbivorous, or carnivorous, or both. 



GEOGRAPHICAL DISTRIBUTION. This family is distri- 

 buted through the temperate climes of the world, different 

 genera and species being peculiar to different countries. 

 Europe is the common centre from which they radiate 

 into other parts of the old world, and from whence the 

 species of that continent are destined to spread to every 

 country which is reached by European commerce. Some 

 of them have already gained a permanent footing in this 

 country, though their range is yet limited. The native 

 species have a general range, from the Great Lakes 

 nearly as far south as the Gulf of Mexico, and from 

 beyond the Mississippi to the sea-coast. One or more 

 species have been already found on the western side of 

 the continent. There cannot be a doubt that other spe- 

 cies, not now known, will be discovered in the United 

 States ; for it would be most extraordinary if the vast 

 area of this country should be found to be occupied by 

 only two or three native species of the family. 



