45 



umbonal region, anterior to the attacament oi tlie ijoste- 

 rior adductor {.v_.ji.Q_. fiR. 26). Witli the remarkable ap- 

 peai-ance of tlie apophyses or tlie shell, the pedal muscles 

 suddenly lose their old attachment in the umbonal region, 

 to become attached to the apophyses through almost the 

 whole length of the latter. After this shifting, which 

 talces place as the young "Ship-worm" begins to bore, the 

 padal muscles no longer form distinct muscles, but wide 

 bands which run from the apophyses to be distributed 

 aroiind the sides of the foot. 



In Teredo, the posterior end of the body, which has 

 usually been described as the "muscular collar", contains 

 a number of highly specialized muscles, some of which are 

 peculiar to the "Ship-wonns", Their general arrangement, 

 and their relations to the palettes and calcareous tube 

 ai-e si.o^vn in figs. 21 and 22. They are divided into two 

 sets, those which manipulate the palettes, and those which 

 are distributed to the siphons. The first set consists of 

 a pair of protractors of the palettes (£.j2. ) , two pairs 

 of retractors of the palettes (r.£. ) and a sin.";le adductor 

 pf the palettes (a_.£. ) . On either side the protractor of 

 the palette in in^orted along the hand! n of tlie palette. 



