According to Roland, the 2nd Mississippi Cavalry was known as the 42nd Mississippi Cavalry on early war rolls. (Soldiers' records show enlistment into the 42nd Mississippi Cavalry at least as late as May 1 1862) I assume that it would be odd for someone enlisting in 1863 to call it the 42nd, but I'm just guessing.
http://www.mississippiscv.org/MS_Units/2nd_MS_Cav.htm
No Halls listed in the 2nd Miss Cav in the Soldiers and Sailors.