Calvert Cliffs Ecphoras

Here are two nice exampes of ecphoras from Calvert Cliffs, MD.  I think the one on the right is the Ecphora quadricostata, but the one on the left I'm not sure about.  Ecphoras aren't that common along the cliffs, usually find only pieces of them.  The one on the left is only one of two like it with the smooth ridges.  Anyone know what type it is?

thanks,
Daryl.