ELYSIID^E. 



flattened lobe, and the gills are arranged in single file on each 

 side of the body. 



S])ecies of Ctcelia. 



fimbriata, Vahl. pallida, Alder and Hanc. 



formosa, Loven. pulchra, Alder and Hanc. 



uiinuta, Forbes and Goodsir. trilineata, Sars. 



Fam. ELYSIID^. 



Body limaciform, clothed with cilia. Tongue narrow; 

 teeth in a single, central series. Tentacles subulate or linear, 

 folded ; eyes sessile, near the bases of the tentacles. Gills 

 in the form of plaits or vessels radiating on the surface of 

 the back. Vent central, dorsal, on the hinder part of the 

 back. 



In this family the respiratory function appears to be per- 

 formed by the entire surface of the body, special organs for 

 that purpose being almost obsolete. It constitutes a portion 

 of the Order Pellibranchiata of Alder and Hancock. 



Genus ELYSIA, Bisso. 



Body with the lateral ridges dilated into wing-like na- 

 tatory appendages. Head distinct, with two conspicuous 

 auriform tentacles. 



Si/n. Actseon, Oken, not Montf. Aplysiapterus, Chiaje. 

 Rhycobranchus, C antra ine. 



Ex. E. viridis, Montagu, pi. 67, fig. 6. 



The auriform tentacles and extended natatory appendages 

 distinguish this genus, which inhabits the laminarian zone, 

 usually on C odium tomentosum and Zoster a marina. 



