I may be wrong on this, and would like if somebody can provide a better identification or verify if the listing I'm giving is correct.
The closest listing I located in my shell identification books, was the "Atlantic Yellow Cowry", or Cypraea spurca acicularis which measures between ½ - 1¼" and found commonly Southern Florida, Yucatan and the West Indies.
However, it's likely this particular species, is identified among the Cowry shell. For images of Cowry shells, click here.
Your "NC cowrie" is a common Atlantic marginella (Marginella apicina), found from NC to Brazil. Grows to 1/2 inch.
Terri K. Hathaway
Marine Education Specialist
North Carolina Sea Grant