98 ANNELIDA. 



Cirratulus (Lamk.). Head indistinct, without any 

 appendages ; feet two-branched, the upper branch 

 alone bearing a long thread-like cirrus. Lurking 

 under stones. 



C. medusa. Fig. 159 ; n. s. 

 tentaculatus. 



Genera imperfectly characterized: apparently of 

 Arenicolana. 



Derris (Adams). Head furnished with a flexible 

 proboscis, and two short tentacles. Inhabiting a 

 membranous tube tapering to a point behind; free. 



D. sanguinea. Pig. 160, n. s. ; and head mag. 

 Branchiarius (Montagu). Body irregular, sub- 

 pellucid, destitute of eyes and tentacles; gills 

 seated on each side ; front four-lobed. 



B. quadrangulatus. Fig. 161'; n. s. 



