THE SEA-SLUGS. 



263 



KEY FOR IDENTIFICATION OF ANIMALS DESCRIBED IN 

 THIS CHAPTER. 



OPISTHOBRANCHS. Usually without shell, gill behind the heart. 



(1) Shell present, one lateral gill. 



Shell concealed, delicate, -\ 



single gill, 2 well- \Aplysia hybrida. 

 developed epipodia J 



(2) Shell absent, gills plumose, placed round anus in mid- dorsal 

 line. 



D. tuberculata, 9 tripin- 



' nate gills, tubercles 

 numerous, round. 



D. johnstoni, 15 tripin- 

 nate gills, tubercles 

 minute, close-set. 



D. repanda, 5 tripinnate 

 gills, tubercles small, 

 distant. 



D. bilamellata, numerous 

 simply pinnate non- 

 retractile gills, tubercles 

 large, unequal. 



D. pilosa, 7 to 9 non- 

 retractile gills, mantle 

 with dense soft papillae. 



Body ovate, depressed,' 

 mantle large, without I 

 processes, coveringhead \-Doris 

 and foot, dorsal ten- 

 tacles retractile . 



Body elongated, mantle 

 small, without pro- 

 cesses, not covering 

 head and foot, dorsal 

 tentacles non-retractile 



Body elongated, mantle 

 small, bearing lateral 

 processes, gills 3, tri- 

 pinnate 



Body elongated, mantle" 

 indistinct, head with 4 

 to 6 processes, gills 7 

 to 9 with lateral ap- 

 pendage at each side . 



Like Polyccra but with- 

 out head appendages, 

 except for 2 on the ten- 

 tacles, and with only 3 

 gills surrounded by pro- 

 cesses 



Goniodoris 



( Gf. nodosa, gills 13, simply 

 ' \ pinnate. 



Triopa claviger. 



-Folycera quadrilineata. 



Ancula, cristata. 



