DAVENPORT. — EVOLUTION OP PECTEN. 



133 



RAY CLASSES 14 



15 



16 



19 



20 



2} 



17 F.F. 18 

 Figure 1. 

 Polygons of percentage frequencies of rays. 



Eddystone. 



Irish Sea. 



Firth of Forth. ♦ 



The centroid verticals are drawn at E., I. S., and F. F., respectively. 



22 



