104 THE ELEMENTS 



larly wrinkled, and waved ; upper valve 

 convex, under flat and perforated at 

 the hinge, through which the liga- 

 ment passes by which it is affixed to 

 other bodies ; inside pearlaceous, and 

 of various changing colours ; green 

 purple, violet or yellow. 



Often to be met with adhering to 

 the common oyster, or ostrea maxima. 



Linn. Trans, vol. viii. page 102. 



a Base, m> ligament perforation. 



Fig. 8th.-\ ENUS DECUSSATA. 

 Shell ovate, with decussate striae, an- 

 gular before ; apeop turned to one side ; 

 umbo placed nearest one end ; hinge 

 furnished with three teeth in one valve; 

 posterior slope very minute and re- 

 tuse ; anterior slope long and narrow, 

 with generally an inner blue margin. 

 The outside is commonly of a plain 

 rusty brown, and marked with purple 

 zigzag lines. 



Linn. Trans, vol. viii. page 88. 



