The Tennessee Adjatent- Generals Report for 1866 list a James Whitendon on the rolls of Company "B" of the 15th TN Cav (CS). Pnonetic misspellings or mispellings caused bylater transcribers who are unfamiliar with writing styles of the period are common on Civil War Muster rolls.
You should be able to obtain his compiled service record(CSR) from the national archives. If in Tennessee, check with your local library for the microfilm collection of CSR's of soldiers who served in Confederate units from Tennessee. Some of the larger libraries have it. Otherwise contact the National Archives. It should contain info on place of birth, etc. to help verify the identity