U. S. B. F.— Doc. 890. 



Plate II. 



OYSTER WITH RIGHT SHELL AND MANTLE REMOVED. 



A anus; A. M., adductor muscle; Au., auricle of heart; D., digestive gland or liver; G., 

 "gills- I intestine; M., mantle; Mo., mouth; O., oesophagus; P., palps; R., reproduc- 

 tive organ; S., stomach; V., ventricle of heart. (Photo from American Museum of 

 Natural History.) 



