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TONGUES OF MOLLUSC A, 



PART III. 



Fig. 17:.'. Granulated Trojh us. 



The Limpet lives on sea-weeds. The animal is large in 

 proportion to the size of its conical shell ; it has a long 



leaf-shaped gill un- 

 der the edge of the 

 mantle. The head has 

 a short proboscis and 

 pointed tentacles, 

 with eyes at their 

 base. The mouth has 

 a horny jaw and a 

 very long tongue, 

 moved by muscles 

 rising from firm ob- 

 jects on each side of 

 it. Fig. 173 represents the tongue beset with recurved 

 hooks, and A shows a portion highly magnified. These 

 recurved teeth are transparent, amber-coloured, and 

 in the Limpet, as in most of the other Gastropods, they 

 are chitinous. The teeth towards the point of the tongue 

 are sufficiently hard to rasp the food ; and it is said that 

 when they are worn down, the part of the tongue support- 

 ing them falls off, 

 and that the waste 

 is supplied by a 

 progressive growth 

 of the tongue from 

 behind, and a har- 

 dening of the teeth 

 in front. The soft 

 reserved portion is 

 coiled in a spiral 

 when not in use. 

 All the species of Patellidse, or Limpets, have the 

 power of making cavities with their foot in the surface 

 of the rocks to which they adhere. The cavity exactly 

 corresponds in shape and size with the mouth of the 



Fig. 173. Tongue of Limpet: A, portion of 

 surface magnified. 



