RADULA OF PULMONATA 



235 



edges ; central strong, tricuspid ; laterals and marginals very 

 long, falciform, arched, unicuspid. 



Aurictdidae : Teeth very small ; central narrow, tricuspid on 

 rather a broad liase ; laterals and marginals ol)scurely tricuspid on 

 a Imse like Succinea. 



Limnaeidac : Jaw composed of one upper and two lateral 

 pieces ; central and lateral teeth reseml>ling those of Helicidae ; 

 marginals much pectinated and serriform (Fig. 141. A). In 



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Fig. 141.^ — Portions of the radiila of 

 A, Limnaea stagnalis L., -with the 

 central tooth and two first laterals, 

 and two of the marginals, very 

 highly magnified ; B, Aticylvs 

 fluviatilis Miill., with two of the 

 marginals very highly magnified ; 

 C, Physa fontinalis L. , with cen- 

 tral tooth and two of the marginals 

 very highly magnified. 



Ancylvs proper the teeth are of a very different type, base 

 narrow, head rather blunt, with no sharp cusps, teeth similar 

 throughout, except that the marginals become somewhat pec- 

 tinated (Fig. 141, B); another type more resembles Limnaea. 



Physidae : Jaw simple, but with a fibrous growth at its 

 upper edge, wliich may represent an accessory plate ; radula 

 with very oblique rows, central tooth denticulate, laterals and 



