After a little internet research and a call to a good friend, I determined that the above is a Florida conch egg casing. Prior to working in Holden Beach, I spent 15 years just an hour north in Wrightsville Beach, NC, and had never seen a casing of this sort. Nor have I ever seen a Florida horse conch in that area. Apparently North Carolina is the northern most range for the Florida horse conch and for whatever reason few are seen around Wilmington, NC. It's southern range is Mexico, and it's Florida's state shell.
Three types of whelks (a similar mollusk) are found in North Carolina - lightning, channelled and knobbed, but these are distinctly different from the Florida horse conch. Whelk egg casings look like coins stuck together in a string, and are a common sight on NC beaches. One is pictured below with the Florida horse conch casing.
Every day on the water is different, and you never know what you might find or see. Come on a tour with us and see for yourself.