AHA! I believe that solves my riddle. Thanks, Bryan!
I wonder if St. Clair's enlistment into Co. K, 14th Arkansas was similar to that of Andrew J. Garner, who also served in the company, and also later ended up in the 2nd Arkansas Cavalry(US). According to Garner, "I had my choice to go with Co. K, 14th Arkansas or look up a limb to be hanged on." That's quite an inducement; I would say.