Fig. 171.'). Section through the 

 oyster along- the line o of Fig 171 C 

 (enlarged twice), a', a", dorsal and 

 ventral branches of the anterior 

 aorta in section; br, artery to gills- 

 c, connective tissue; ff , giils in sec- 

 tion; g , internal cavities of I lie gills- 

 ffe, egg-gland ; j, i, cross-sections of 

 tHe intestinal tube; /, liver- mt 

 mantle; sb, suprabrancliial or water 

 spaces above the gills; st, stomach- 

 vc, vena cora. After Ryder 



Fig. 1 71 c. The oyster-drill. 

 (Natural size.) 



mantle; P, pa ] p; ills!lAfter Ryder'. 



the , , efrf?S are formed: 

 > adductor 



< 

 heart; mt 



[To face page 833.] 



