TEREDO. SABELLA. 37 



valves at each end, and penetrating through 

 wood. There are four species. 



" Sahella is the last genus, and a very re- 

 markable one. The species are twenty-five, 

 several of which are British, (Plate 8.) 



" Shell tubular, formed of sandy and calca- 

 reous particles, agglutinated, and inserted in a 

 membranous sheath. Sahella Belgica is found 

 in Britain. S. chrysodon is found buried in 

 sea-sand, often several inches long ; it is covered 

 with fragments of shells, and so brittle that it is 

 not easy to obtain a complete specimen. 



" We have now finished our Linnaean genera, 

 and here we must pause for the present. If you 

 wish for any assistance in your study of the 

 thirty-six examples that I have given you, I 

 shall be ready to afford you both any help that 

 lies in my limited power." 



