xi PHYLUM MOLLUSCA 293 



Gastropoda, which, however, they share with some Amphi- 

 neiira and with the Cephalopoda, is the possession of an 

 odontophore and radula, situated in a thick-walled chamber, 

 the buccal cavity, into which the mouth opens. From the 

 floor of the cavity rises an elevation, the odontophore, which 

 is somewhat elongated in the direction of the long axis of 

 the body, and compressed laterally. Over the summit of 

 the odontophore runs longitudinally a narrow strap-like 



pul.v 



eiur 



FIG. 168. Pulmonary cavity and related parts in a slug (Limax). aort. aorta ; 

 aur. auricle ; neph. nephridium ; peric. pericardium, laid open ; put. ap. pul- 

 monary aperture ; pul. v. pulmonary vein with its ramifications ; red. rectum ; 

 ur. ureter ; vent, ventricle. (After Pelseneer.) 



body, the radula or lingual ribbon (Fig. 169, rad.\ beset 

 with numerous minute horny teeth arranged in transverse 

 rows. Posteriorly this toothed ribbon extends into a 

 narrow curved pouch, the radular sac (rad. sac.), extend- 

 ing backwards from the posterior and lower aspect of the 

 buccal cavity. Anteriorly it does not extend beyond the 

 odontophore prominence. The latter contains cartilages 

 (cart.) serving for the support of the whole apparatus, 

 and is capable of being extruded, with the radula which 



