232 



RADULA OF PULMONATA 



CHAP. 



something more than a mere weak reproduction of the marginals. 

 There are no true laterals. The Limacidae show a further stage 

 in the transition. Here the central tooth has a definite shape of 

 its own, tricuspid on a broad base, which is more or less repeated 

 in the first laterals ; these, as they approach the marginals. 



Fig. 138. — Portion 

 of the radula of 

 Glandina trun- 

 cata Gmel. x 40. 



gradually change in form, until the outer marginals are again 

 thoroughly Testacellidan.^ This is the general form of radula, 

 varied more or less in different genera, which occurs in I^anina, 

 Helicarion^ Limax^ Parmacella^ and all the subgenera of Zoiiites. 

 It is certain that some, and probable that all of these genera will, 



Fig. 139. — Portion 

 of the radula of 

 Rh y t id a Kra uss'ii 

 Pfr., S. Africa. 

 x25. 



on occasion, eat flesh, although their usual food appears to be 

 vegetable. The jaw is more powerful than in the Selenitidae, 

 but never so large or so strongly ribbed as in Helix proper. 



When we reach the Helicidae, we arrive at a type of radula 



1 In some cases (e.g. Hyalinia inornata) the laterals are very few, while in 

 Zonites laevigatus the first side tooth is more of a marginal than a lateral. 



