37 



repi'esents the left palette of a specimen 5 mm. lonf^. It 

 consists of a series of seven funnel-shaped structures 

 wliich have been foi'med and cemented in succession to the 

 handle. The formation of the palettes is as follows :- 

 In specimens still less than 1 mm, long, the mantle of the 

 posterior region has foi-med a duplicature (figs. 4,7)which 

 project over the base of the siphons. At the anterior 

 portions of the sides of the space tlius formed, the epith- 

 elium of either side pushes forwards. In tlie invagina- 

 tion thus formed, the handle of the palette is formed, and 

 projects into the "collar" space. The lining walls of the 

 sides of the co'llar space secrete the funnel-shaped ])ieces 

 which are cemented to the handle. New larger pieces are 

 added at the anterior end, and those first formed may be 

 broken off. In Teredo, the paddle part of the palette is 

 a solid piece and not divided into pieces, as has just 

 been described for Xylotrya. Strictly speaking, the seg- 

 ments of a palette are semi-circular when seen on end. 

 lYhen the two palettes are brought together in closing the 

 tube, they form a truncated cone. 



