MOLLUSCOIDEA — BRACHIOPODS 



199 



Fig. 81. — Productus semireticulatus Martin, from the Pennsylvanian of Indiana. 

 Three views of one individual, natural size. A, pedicle valve ; B, brachial valve 

 with umbo of pedicle valve showing over edge of hinge line. C, side view. (After 

 White.) 



Platystrophia (Fig. Si). Ordovician to Silurian. 



Hinge line long. Both valves very convex, with a strong 

 median fold in the brachial valve and a corresponding deep 

 sinus in the pedicle valve. Entire surface covered with broad, 

 strong, sharp plications (whence the name from Greek platys, 

 wide, -{-strophos, a band). Shell impunctate but with a granu- 

 lose surface. 



