Arenicola assimilis 



125 



,j^^«s^;^?;)<=*«^__ 



St.O. 



Fig. 55. — A. assimilis, co-type, from 

 Uschuaia. Anterior end, dorsal aspect ; 

 the prostoniinm is in a state of normal 

 extension. 



-St.O. 



i'iii. 56. — A. assimiliji var. affinia, from Otago 

 Harbour, N.Z. Anterior end, dorsal aspect ; 

 the buccal mass and pharjTix are fully pro- 

 truded, and the prostomiuni is well extended 

 St.O. External aperture of statocyst. 



Fig. 57. — A. assimilis! var. affinis, from the 

 Falkland Islands. Anterior end, dorsal 

 aspect ; showing prostomium very fully ex- 

 tended, exposing to view the median pos- 

 terior part (P.), which is usually hidden in 

 the nuchal organ ; M. Median ; L. Lateral 

 lobe of prostomium ; ST.O. External aper- 

 ture of statocyst. 



Fig. 58. — A.assimUigx&T. afiniti, from Susanna 

 Cove. Anterior end, dorsal aspect ; the 

 lateral lobes of the prostomium are larger 

 than usual, but are still considerably smaller 

 than those of A. 2>iisitla (rf. Fig. 48). 



