CHAPTER X. 



THE FRESH-TV ATEB CLAM. 



1. Notice the two ends of the shell. In what 

 respects do they differ ? 



2. The edge on which the two parts of the shell 

 are attached to each other is the dorsal margin. 



3. On the dorsal margin, find a pair of eleva- 

 tions, one on each part of the shell. These are the 

 umbones. 



4. Between the umbones, and extending from them 

 in one direction, find a smooth band, the hinge liga- 

 ment. What is its use? 



5. Hold the shell with the dorsal edge upward, 

 the hinge ligament toward you. When in this posi- 

 tion the end of the shell toward you is the posterior 

 end, the end away from you is the anterior end, the 

 part of the shell toward your right is the right valve, 

 and the part of the shell toward your left is the left 

 valve. 



6. Notice the epidermis, covering the shell. The 

 lines running concentrically around the umbo and 

 extending over the entire shell are the lines of 

 growth. 



7. Draw a dorsal view of the shell. Draw a side 

 view of the left valve. 



Interior of the Shell. 



1. Notice the color and the interior surface of the 

 shell. Can you see the lines of growth? 



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