Joe, Lynda, & others:
Capt. J. P. Montgomery was from Jack County, Texas and originally commanded Co. D of the 25th Texas Cavalry. Sometime in 1863 a squadron (company) of the now consolidated 24th/25th Texas Cavalry was attached to the General Headquarters of the Trans-Mississippi Department in Shreveport and acted as escorts and couriers along with the 1st T-M Cavalry Battalion. They are shown on an organizational chart of the T-M Dept. in September and December 1864. The remainder of the 24th/25th was in the Army of Tennessee at the time.
The squadron numbered about 130 (present & absent) in Dec. 1864. I'm still looking for Pvt. Calvin Davis.
This info is in the Official Records, Series I, Vol. 41, Parts 3 & 4. One chart showing the unit is on p. 1141, part. 4.