140 



CLASSIFICATION OP 



containing animals commonly met with. The Nudi- 

 branchiata* or Slugs with naked gills, have the gills 

 placed on the outside of the body, expanding freely in 

 the water, like the tentacula of the Sea Anemone. Few 

 marine animals offer more beautiful forms, gaily orna- 

 mented with colours, and 

 fringed with tentacula; while 

 their breathing apparatus 

 often displays the most 

 elaborately-branched leaves, 

 placed like the petals of a 

 flower. The Tectibranchiata, 

 or Slugs with covered gills, 

 are animals of a something 

 similar aspect, apparently 

 soft Slugs, but often fur- 

 nished with an internal 

 shell. In these the gills are 

 placed on one side of the 

 body, under the deep folds 

 of the mantle. Among sea- 

 weeds, near low-water-mark, 

 a deep purple Mollusc of 



this group may be found, called Aplysia. It is one or 

 two inches long, with a snail-like body, a prominent 

 head, furnished with four ear- shaped tentacula, two 

 near the tip of the snout, and on the forehead two more, 

 at the base of which are seen a pair of small, peering 



* A monograph of the British species of this group, illustrated by 

 exquisitely beautiful plates, is in course of publication (through the 

 Ray Society) by Messrs. Alder and Hancock. 



