EXPLANATION OF PLATE XLVI. 



GRYPHAEA MUTABILIS Morton, p. 452 



i. External view of a nearly complete valve. 



Marshalltown clay-marl; near Swedesboro, (180). 



GRYPHAEA DISSIMILARIS n. sp., p. 453 



3-4. Two views of a nearly complete individual retaining both 

 valves. 



Hornerstouin marl; near Woodstown, (181). 



974 



