16 LIMACID^E. 



REMARKS. This genus was instituted by Ferussac in 

 1821, but had been previously designated by Blainville 

 under the name of Veronicella, who subsequently, how- 

 ever, merged them both in the genus Onchidium of 

 Buchanan. There can be no doubt of the propriety of 

 separating the terrestrial species from the marine species, 

 all of which were combined in the original genus Onchi- 

 dium, to whichever group we may assign that name.* 

 Their habits, form, tentacles, and their anatomical de- 

 tails are all different. 



The contractility of the animal is very great. When 

 extended it is very long and slender, and smooth or 

 faintly reticulated, three or four times as long as when 

 contracted ; in which latter state it has an oblong form, 

 equally rounded at both ends, and its surface is coarsely 

 wrinkled, granular or tuberculated. The lower tentacles 

 are generally bifurcate at tip, or rather there is a sup- 

 plementary tentacle or spur, which can be protruded just 

 short of the point of the tentacle ; sometimes the tips are 

 said to be even palmate. 



It lives in families under stones and trunks of trees, 

 and sometimes buried in the earth. It is capable of 

 retiring from damp places, and sometimes inhabits very 

 dry localities. It issues forth in the night and on wet 

 days, when it may be found upon trees. Its movements 

 are very rapid. 



* I employ in this instance the name selected by Dr. Binney, though both 

 the names of Blainville and Buchanan have priority. G. 



