66 



Y.I. KANTOR, A. MEDINSKAYA AND J.D. TAYLOR 



Fig. 11 Radulae of Crassispirinae. a, Crassispira (Monilispira) pluto, scale bar = 20pm b, Crassispira (Striospira) kluthi scale bar * 

 (Crassiclava) turricula scale bar = 30 pm d, C. (C.) turricula scale bar = 20 pm. 



10pm c. Crassispira 



continuous with that of the proboscis wall. The wall of the 

 rhynchodeum in its posterior part is muscular and free and much 

 thicker than to the anterior. This posterior part of the rhynchodeum 

 is able to evert. Powerful retractor muscles are attached at the point 

 where the rhynchodeal epithelium changes; these run along the 

 rhynchodeum and are attached to the buccal mass. 



In the retracted position, the proboscis is rudimentary (Fig. 13), 

 being only about twice as long as than the radular tooth length. The 

 mouth opening is very narrow. There is no anterior buccal tube 

 sphincter and the sac-like enlargement of the buccal tube is small. At 

 the base of the enlargement there is an intermediate sphincter, which 

 lies at a distance of about three radular tooth lengths from the mouth 

 and posterior to the proboscis. The buccal tube forms a loop poste- 

 rior to the proboscis and widens greatly before opening in the buccal 

 mass. 



Buccal mass and oesophagus 



The buccal mass is medium-sized, and located to the posterior of the 



mebt 



Fig. 12 Crassispira (Crassiclava) apicata (Reeve, 1845). 



