90 



BOYS AND GIRLS IN BIOLOGY. 



longs, if yon hold the small end toward you, and the 

 hinge upward (Fig. 89). These four straps are fastened 

 quite near the ends, close to the upper, or dorsal border 

 — two on the right side and two on the left (Fig. 90). 

 They are made of an elastic substance called muscle, 

 that stretches or lengthens when the animal wants to 

 open its shell, and contracts, or shortens, when the 



Fig. 91. 



Mark made by Edge of Mantle — 

 Left Half of Shell. the Palial Line. 



Front Muscle — Lower Ventral Opening Mantle, before it is 



Anterior Ad- and its Cilia, or Lashes. lifted up. 



DUCTOR. 



shell closes. Now, we are ready to break into the 

 house, since we have found where the fastenings are. 

 If you lay the mussel down on his right side, the large 



