22 



dorsal side of the odontopliore under tlie coinineueemciit 

 of the gullet (fig. 12). This cavitj- narrows beliiud into 

 the radular sac. 



(h) Within the dorsal and ventral outer lips an 

 inner lip is present on either side as an upwardly growing 

 fold (fig. 6). Boutan refers to this pair of lips as " une 

 levre en forme de fer a cheval.'' These two lips can be 

 approximated so as to close the mouth almost entirely. 

 A median papilla, or "licker," belonging to the 

 odontopliore, projects between the lips so as to com- 

 pletely mi the chink between them when the mouth 

 is closed. 



(c) The dorsal palatal plate is a chitinous sub-e})ithelial 

 thickening forming an arch over the region of the inner 

 lips. It imparts firmness to the lip and also serves to 

 lift the tissues connected with it out of reach of the 

 rasping radula. It is prolonged into two pairs of 

 expansions, one pair dorso-lateral and one pair ventro- 

 lateral (fig. 11). This plate is most probably a pair of 

 jaws united by a median dorsal piece. 



[d) The front end of the odontopliore or rasping organ 

 projects into the palatal section of the buccal cavity from 

 its postero-ventral wall, and the front end of the radula, 

 a horny tooth-studded ribbon, occupies a narrow median 

 strip on this projection (fig. 12), extending backwards on 

 the posterior part of the odontophore cushion, which is 

 placed beneath the floor of the post-palatal section of the 

 buccal cavity {a above) underlying the gullet. The 

 e])itlieliuni covering the tip of the odontophore, anterior 

 to the radula, has grown out into a transversely ribbed 

 projection, which is the papilla, or " licker." 



(c) The sub-lingual pouch is a recess below the front 

 end of the odontophore (fig, 6). It is found in Chiton 

 and many other forms. In Patella it is lined bv 



