Smithsonian Report, 1%^ Hav 



Plate 2 



Elcclromuicrugrapli of a carbon replica of a sieve-plate covering the end of a pore canal of 

 Robulus midwayensis (Plummer), x 140,000 (from Hay, Towe, and Wright, 1962- micro- 

 graph by K. M. Towe). ' 



