47 



palettes, the palettes are pushed forcibly into the end of 

 the tube so as to completely close the latter. The outer 

 ends of the paddles are brought together by the sides of 

 the tube, while the anterior ends of the handles are sep- 

 arated. As the disturbance disappears, the palettes seem 

 dislodged by the ventral retractors, and retraction seems 

 to be completed by the long muscles attached to the ends 

 of the handles. At the same time, by the action of the 

 adductor of the palettes, their paddles are separated, so 

 as to permit the extension of the siphons by an inflov/ of 

 blood. 



From this description, it is seen that the end of 

 the tube of Teredo is homologous with tlie pallial sinus 

 of typical Lamellibranchs. The same siphonal muscles are 

 present as in other forms, while the muscles of the pal- 

 ettes are peculiar to the "Ship-worms". 



