Cecil,
I only find one card on John N Bryan (spelled Bryant on return) Enlisted at Dallas,Texas Jan 21.1861 for 1 year in Capt Dammon's Company, Darnell's 18th Texas Cavalry Regt. This company became Company C in May 1862.
From Handbook of Texas online: He joined Col Nicholas H Darnell's 18th Tex Cav Regt. in the winter of 1861 and served until late 1862 when he was discharged because of his age and poor health.
Mike