432 ASCOGLOSSA — NUDIBRANCHIATA chap. 



the Cladohepatic Nudibranchs, while the Pleurobranchidae form 

 a somewhat similar link between the Holohepatic Nudibranchs 

 and the other Tectibranchiata. 



Fam. 1. Oxynoeidae} — Animal long, tentacles auriform, 

 epipodia large, simple, or wing-like, a ctenidium and branchial 



chamber on right side, shell small, thin, 

 slightly spiral, not covering much of 

 the body. Genera: Oxynoe (^=Lopho' 

 cercus)^ Lohiger. 



Fam. 2. Hermaeidae. — Body de- 

 pressed, cerata in several rows, no 

 branchiae, no shell. Genera : Hermaea^ 

 Phyllohranchus^ Stiliger^ Alderia. 

 Fig. 288.— Raduia of one of Fam.. S. ^lysudae. — Body depressed, 



Mont^'T^oh^^'''' ''''^''^'' head rather elevated, tentacles auriform, 

 sides of body dilated into two large 

 wings, which enclose branches of the liver and sometimes fold 

 over the dorsal surface, no branchiae, no shell. Genera : Elysia^ 

 Thridachia^ Placohranchus. 



Fam. 4. Limapontiidae. — Body slug-like, liver scarcely 

 ramified, no branchiae, shell, or appendages. Genera: Lima- 

 pontia, Aetaeonia, Cenia. 



Sub-order III. Nudibranchiata. — Shell absent in the adult, 

 no ctenidium proper, or osphradium, cerata dorsal or dorso-lateral, 

 nervous system concentrated, kidney not compact, ramified, penis 

 retractile, jaws and raduia usually present. 



Section I. Cladohepatic a. — Cerata usually latero-dorsal, 

 elongated, or arborescent, buccal mass strong, jaws present, liver 

 generally ramified, rami generally entering the cerata. 



Fam. 1. Aeolidiidae. — Body slug-like, head with tentacles 

 and rhinophores, dorsal area with rows of cerata, which usually 

 contain sting-cells, raduia variable. Genera: AeoUs, Cratena, 

 Tergipes^ CorypTiella^ Favorinus^ Facelina^ Flahellina^ Fiona, 

 Grlaucus, Janus, Hero, with many sub-genera. 



Fam. 2. Tethymelibidae. — Body slug-like, large, cerata very 

 large, no sting-cells, head large, cowl-shaped, no tentacles, rhino- 

 phores much foliated, no raduia. Genera : Tethys, Melibe. The ' 

 cerata of Tetliys, which are capable of independent movement 



1 This family has also been classified with the BuUoidea and with the 

 Aplysioidea. 



