267 



CHAPTER XLIII. 



[This Chapter, accidentally omitted in the printing, should appear between 

 Chapters V. and VI.] 



TUBE-MAKERS. THETR CHARACTERS AND HABITS. THE ' WATERING-POT.' 



GASTROCH^NA. — SAXICAVA. PETRICOLA. — VENERUPIS. 



GASTKOCH^NID^. 



The British moUusca included by Professor Porbes under 

 this appellation are all, like the Pholades, borers : they all 

 make their dwellings in the rocks. In their case, however, 

 there is no probability of the shell being used as a rasp, for 

 its outer surface is smooth in every species. In tlie general 

 oblong form of animal and shell the GastroclmnidcB resemble 

 the PholadeSj and, like the latter, have a double siphon at 

 the upper or hinder end; the tongue is not round and 

 sucker-like, but sharp, curved, and pointed, and it is pro- 

 truded through a small hole in the mantle, which is other- 

 wise entire. In all the shells of this family the valves are 



