The NPS Soldiers and Sailors Database lists the 40th, 42nd 46th and 48th Arkansas Infantry Regimennts. All except the 46th simply say "Units of the Confederate States Army" by Joseph H. Crute, Jr. contains no history for this unit. The 46th has the following history.

46th Regiment, Arkansas Infantry 46th Infantry Regiment was formed in the spring of 1864 with men who had served in other Arkansas units that were not reorganized after the fall of Vicksburg. Serving unattached as mounted infantry in the Trans-Mississippi Department, the regiment participated in Price's Missouri operations and saw some light action in Arkansas. It was included in the surrender on June 2, 1865. Colonel W.O. Coleman was its commander.

The Gerdes Site seems to only go up to the 39th )(Cocke's) Arkansas Infantry Regiment.

Gerdes does list the following a Cavalry Regiments:

45th
46th
47th
48th

Are these high numbered Cavalry Regiments really Mounted Rifles that were listed as Infantry on the NPS site?