Hey there Jay,
It sounds like you have a calendar that you would like to delete from from the Calendars app. Take a look at this info from the article named:
iCal 5.x: Delete a calendar or reminder list
http://support.apple.com/kb/PH4720
Delete a calendar or calendar group
- Click Calendars (in the top-left corner of the iCal window), and then select the calendar or calendar group you want to delete by clicking its name in the Calendars pop-up list.
- Choose Edit > Delete.Deleting a calendar group deletes all the calendars contained in the group.
If it is not in the Calendars app, but in Mail, would you mind elaborating on where you are seeing it in the application?
Thank you for using Apple Support Communities.
Take care,
Sterling