56 POLYCERIN^E. 



processes protecting the branchiae, which are large and 

 plumose. A single species, from the Red Sea. 



Genus ceratosoma, Adams and Reeve. 



Body elongate, smooth. Tentacles clavate, non-retractile, 

 without sheaths ; forehead simple, rounded. Gills plumose ; 

 hack produced behind into a single, elevated, conical, ap- 

 pendage. 



Ex. C. cornigerum, Adams and Reeve, pi. 63, fig. 3. 



In Ceratosoma the tentacles are bulbous at their bases, 

 the body is smooth, and the foot is linear and grooved ; in 

 our figure the proboscicliform mouth is exserted, which is 

 frequently the case in these animals just- before death. 

 These animals, which somewhat resemble Polyccra, are 

 inhabitants of tropical seas, where they are found crawling 

 on the corallines and madrepores. 



Species of Ceratosoma. 

 cornigerum, Adams and Reeve. trilobatum, Gray. 



Genus ACANTHODORIS, Gray. 



Tentacles dorsal, retractile within denticulated sheaths. 

 Branchial plumes large, spreading, not retractile. 



Ex. A. pilosa, Midler, pi. 63, fig. 4. 



The clubs of the tentacles are beautifully laminated, and 

 the mantle is covered with long soft processes ; the principal 

 feature in this genus, however, is the fact of the branchial 

 plumes being non-retractile. The two species known are 

 from the coasts of Europe. 



Species of Acanthodoris. 

 pilosa, Midi. subquadrata, A Ider and Hanc. 



