So, it seems that the Shark Eyes and Moon Snails are two different species.
This is the Northern Moon Snail, Euspira heros.
Unfortunately, I don’t have an example of Neverita duplicata, the Shark Eye, since getting any of these intact on the beach is hard. The Shark Eye “can easily be distinguished [from the Northern Moon] by the heavy brown or purple callus” say Jacobson and Emerson in their classic Shells from Cape Cod to Cape May. The callus on this is neither heavy, nor brown, nor purple.
It’s easier to link to an illustration of the callus than to describe it.
Backyard and Beyond 
Lady with beautiful grey streaks has her hair pulled back into a bun. That is my description :;
Lovely and different. Don’t see much of these beauties on the upper West side.