40 PLEUROBRANCHIN-ffi. 



Genus neda, H. and A. Adams. 



Tentacles dorsal, truncate ; labial appendages transversely 

 prolonged, acuminate, united anteriorly, and forming a 

 large, semilunar, oral veil. Mantle small, with a truncate 

 anal siphon on the hinder dorsal surface. Foot very large, 

 extending beyond the mantle, rounded behind, truncate in 

 front. 



Shell none. 



Syn. Pleurobranchus, sp. Cuvier. 



Ex. N. luniceps, Cuvier, pi. 61, fig. 1,1, a. 



In this genus the oral veil is laterally dilated, forming 

 a large semilunar shield over the proboscis, with the sides 

 produced and angulated; the mantle is small and covers 

 only the dorsal region, and the vent appears to be tubular 

 and situated centrally at the hind part of the back. 



Genus PLEUROBRANCILEA, Meckel. 



Tentacles dorsal; eyes none; labial appendages united 

 by a narrow, transverse, oral veil. Mantle indistinct, indicated 

 by a narrow band on the right side ; anal orifice above the 

 gill. Foot narrow. 



Shell none. 



Syn. Pleurobranchus, Oken, not Cuv. Cyanogaster, Ru- 

 dolphi. Pleurobranchidium, Blainv. 



Ex. P. Meckelii, Leve, pi. 61, fig. 2, 2, a. 



In this genus the mantle-margin is not so developed as in 

 Pleurobranchus, and does not extend beyond the foot ; the 

 plume-like gill is not so prominent, and is less deeply divided ; 

 there is no indication of a shell, and the vent is situated 

 above, and not behind, the gill. 



