d 



Fie. 74. 



Radulae of various glossophorous Mollusca. A, diagram showing mouth, oesophagus, and 

 lingual apparatus of a Gastropod in median sagittal section, a .1, lower lip ; a.w, upper lip ; 6, - 

 jaw of the left side ; c, outer surface of the snout ; d, oesophagus ; e, fold in the wall of the 

 oesophagus behind the radular sac (n) ; /, anterior termination of the radula and its bed, the 

 point at which it wears away ; g, base of the radular sac or recess of the pharynx ; h, cartila- 

 ginous piece developed in the floor of the pharynx beneath the radula, and serving for the 

 attachment of numerous muscles, and for the support of the radula ; i, anterior muscles ; k, 

 posterior muscles attached to the cartilage ; I, muscle acting as a retractor of the buccal mass ; 

 m, muscle attached to the lower lip ; n, posterior extremity of the radular sac ; o, the bed of 

 the radula or layer of cells by which its lower surface is formed ; p, the radula or lingual 

 ribbon ; q, opening of the radular sac into the pharynx or buccal cavity ; r, cells at the extreme 

 end of the inner surface of the radular sac which produce, as a cuticular secretion, the rows of 

 teeth of the upper surface of the radula. 



B, radula or lingual ribbon of Paludina vivipara, stripped from its bed. 



C, a single row of teeth from the radula of Trochus cinerariiis (Rhipidoglossate); formula : 

 co.5.1.5. oo. 



/), a single row of teeth from the radula of lanthina fragilis (Stenoglossate) ; formula : 

 oo .0. oo . 



E, a single row of teeth from the radula of Trachydermon eineretim (Amphineura) ; formula : 

 3.1.2.1.1.1.1.1.2.1.3. 



F, a single row of teeth from the radula of Patella vvlgnto. (Docoglossate) ; formula: 

 3.1.2.0.2.1.3. 



G, a single row of teeth from the radula of Cypraca Jielvola (Tacnioglossate) ; formula : 

 2.1.1.1.2. 



H, a single row of teeth from the radula of Nassa annulata (Rachiglossate) ; formula: 

 1.1.1. The common Whelk is similar to this. 



90 



