SHUMARD—PERMIAN FOSSILS. 291 
Propuctus Mexicanus, W. sp. 
yo _ concentris 
which give to the ribs at the points of crossing a handsome 
subnodulose character. The concentric folds are not as prom- 
ease be iacegt ch the selen SNeEN ses ah Stee ae 
fac a Antprecctpte om Sigg apn border are 
