80 



Ty. typhlosole. 

 Ven. ventricle. 

 A anterior. 

 P posterior. 

 D dorsal. 



V ventral. 

 E external. 

 I internal. 

 E right. 

 L left. 



Plate I. 



Fig. 1. Cockle with the foot and siphons moderately 

 extended, seen from the right side. Nat. size. 



Fig. 2. External anatomy ; the left valve and part of 

 the left mantle lobe have been removed. Nat. 

 size. 



Fig. 3. General anatomy ; the right valve and mantle 

 lobe have been removed, and the right wall of 

 the viscero-pedal mass cut away to expose the 

 intestine ; the right wall of the pericardium is 

 cut away ; the right branchiae are removed. 

 Magnified 2|- diameters. The figure is slightly 

 diagrammatic ; the convolutions of the intes- 

 tine are represented as pulled apart, and for 

 clearness, as being less in diameter than the 

 magnification of the figure warrants. Their 

 exact relations are seen in the section repre- 

 sented in fig. 11. 



Plate II. 



Fig. 4. Section passing through the ureters transver- 

 sely to the long axis of the shell, and cutting 

 the branchiae obliquely. X 3 diam. 



Fig. 5. Transverse section through the bases of the 

 siphons. X 4 diam. 



Fig. 6. Transverse section through the posterior adduc- 

 tor muscle. X 4 diam. 



