PLATE V. 



Feesh-water Mussel {Anodonta Cygnea), 



Dissected so as to show its muscular and nervous systems, as well as certain other 

 organs in relation with them. 



The animal has been taken out of the shell ; the gills have been 

 removed on the left side, as also the mantle, tog-ether with the 

 labial tentacles and parts of the pericardium, and of the organ of 

 Bojanus of the same side. 



a. Eight mantle lobe, free along its ventral edge. 



a. Fimbriated portion of mantle corresponding to the inlet by 



which water is drawn into the branchial cavity. 

 a'\ Dorsal raphe along which the two halves of the mantle 

 meet, and are more or less united. 



b. Foot. 



c. Gills of right side. 



c'. Process passing from external gill to join the mantle, just 

 where its fimbriae cease and its anal region commences. 



d. Anterior adductor, 



e. Posterior adductor. 



/. Posterior retractor of the foot, passing to be inserted, into 

 either valve, anteriorly and superiorly to the posterior ad- 

 ductor, the scar or muscular impression of the two being 

 more or less confluent. Its muscular expansion in the foot 

 is especially well developed along the free or ventral edge of 

 the foot, but it inter-digitates very freely with the pro- 

 tractor pedis, though it lies for the most part at a lower 

 level than that muscle. 



