20 



GOMPA RA TIVE ANA TOM Y 



CHAP. 



FIG. i29. Teredo Navalis in its boring, 

 ventral aspect (after Meyer and Mobius). 

 The centre is omitted, the calcareous tube 

 is for the most part uninjured. 



l~ 



FIG. 30. Shell of Aspergillum (Bre- 

 chites) vaginiferum, dorsal view, a, An- 

 terior; ;>, posterior; d, right; s, left; 1, 

 siplional aperture of the pseudoconch; 2, 

 pseudoconch (calcareous tube) ; 3, true shell 

 embedded in the pseudoconch ; 4, anterior 

 aperture of the pseudoconch. 



