VIII 



RADULA OF PULMONATA 



235 



edges ; central strong, tricuspid ; laterals and marginals very 

 long, falciform, arched, unicuspid. 



Aurieulidae : Teeth very small ; central narrow, tricuspid on 

 rather a broad base ; laterals and marginals obscurely tricuspid 

 on a base like Succinea. 



Limyiaeidae : Jaw composed of one upper and two lateral 

 pieces ; central and lateral teeth resembling those of Helicidae ; 

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



ig'Smmmmp 



Fig. 141. — Portions of the radula of 

 A, Lhnnaea stagnalis L., with the 

 central tooth and two lirst laterals, 

 and two of the marginals, very 

 highly, magnified; B, Ancylus 

 flvviatilis 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. 



Ancylus 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. 



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

 upper edge, which may represent an accessory plate ; radula 

 v/ith very oblique rows, central tooth denticulate, laterals and 



