﻿FRESH-WATER MUSSELS. 



35 



mussel, it is necassarj to pass a sharp blade between 

 the valves, and cut through the muscles, before the valves 

 will open. Tliese muscles are called the adductor viuscles^ 

 and the scars or imjDressions on the valves are called the 

 adductor muscular iiRjyressions. Yerj close to the adductor 

 muscular impressions are seen smaller impressions, and these 

 indicate ^vhere the muscles are attached which move the 

 foot. These muscles are called the ])edal muscles, and the 

 impressions are called \h.Q jpedal muscular impressions. One 

 occurs just behind the anterior adductor impression ; the 

 other will be found just above, and in front of the posterior 

 adductor impression. 



Fig. 39.— The Eight Valve of a Fresh- Water Mussel.— e, Cardinal Teeth : I, Lateral Tooth ; 

 ^i, Ligament ; aa. Anterior Adductor Impression; 7)«, Posterior Adductor Impression; 

 ap. Anterior Pedal Muscular Impression ; -pp^ Posterior Pedal Mnscular Impression ; 

 7>, Pallial Line. 



34. Besides these marks, the pupil w^ill see a delicate 

 aud slightly irregular line running from the anterior to the 



