RUXCINA. 43 



posterior portion of the back beneath the margin of the 

 mantle. Generative organs on the right Bide. 



Shell none. 



These animals appear to partake of the characters of the 

 Pleurobranchtdcs and Bullida, and to form, with the 

 Tlivllidians, a transition group between the Tectibranchiate 

 and Nudibranchiate Gasteropods; in the position of the 

 gills they approach the Pleurobranchida, but they have no 

 tentacles, and in the peculiar testaceous gizzard and frontal 

 lobe they resemble the Bullida. 



Genus RUNCINA, Forbes. 



Body depressed, Hmaciform, smooth. Tentacles none; eyes 

 sessile on the broad cephalic disk. Mantle distinct, oblong, 

 tough. 



Shell none. 



Syn. ? Pelta, Quatrefages (young), not Beck. 



Ex. K. Hancocki, Forbes, pi. 61, fig. 5. 



This curious little genus is probably the same as the 

 Pelta of Quatrefages, which is described as having a 

 similar armed gizzard, and may have been founded on a 

 young specimen of Buncina, in which state the gills are 

 possibly not apparent. The only species known is found in 

 pools left at low water, where they are seen crawling on the 

 tufts of H//j)/tea jpurpurascens infested with Diatomacece 

 upon which they probably subsist. 



Sjiecies of Runcina. 

 ? coronata, Quatref. Hancocki, Forbes. 



