DAVENPORT. — EVOLUTION OF PECTEN. 



157 



DIX F. 



Diameter and Dorso-ventral Diameter. 



Lower Valve. 



M = 87.594 ± .325 ; a = 10.87 ± .231. 



89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 110 111 112 115 



1 

 3 

 5 

 4 

 2 

 7 

 4 

 5 

 7 

 10 

 11 

 10 

 10 

 20 

 15 

 16 

 19 

 26 

 27 

 24 

 31 

 26 

 20 

 26 

 28 

 29 

 29 

 33 

 16 

 19 

 7 

 6 

 3 

 5 

 ■i 

 2 



^508 



20 24 19120 9 15 13 19 12 10.13 20 19 7 11 6 



