Jim; in the History of Adair, Sullivan, Putnam and Schuyler Co.'s, Mo. by Goodspeeed Pub., 1888, I did not find much under the Schuyler Co. section regarding mustering in dates. (It would be worth another look.) In the Sullivan Co. part (and I did not look at the other two counties) on page 103 it mentions that in September 1861 the men in Sullivan Co. made Thos. H. Flood their Captain and they went south and joined Captain Sandusky's Linn Co. group "...and joined Gen. Price's forces at Lexington, were mustered into service by Lieut. Col. Samuel Farrington, and attached to the Third Regiment, Col. E.W. Price, Third Division, Gen. John B. Clark, Missouri State Guards.....At the expiration of the term of enlistment in the spring of 1862, quite a number of the men enlisted in the regular Confederate service, under Capt. P. C. Flournoy,...and surrendered with him at Fort Blakely...."
In The History of Linn Co., Mo.; Birdsall & Dean 1882 on page 347 in referencing the combined Co.'s of Captain Wm. Sandusky and Capt. Thos. H. Flood it states in part: "...Here they crossed the Missouri, and then passed on up the river to Lexington, where General Price's army was met, and where the men were sworn into the state Guard, to serve six months from September 12, unless sooner discharged." (This would have been in 1861.) Jim Magee previously provided me with a copy of a roster list of Captain T.H. Flood's Company [G], 3rd [Infantry] Regiment, 3rd Division, Missouri State Guard, dated 23 October 1861 at Neosho, Missouri. The next sentence reads: "All enlistments were at Lexington, Missouri on 17 September 1861 unless otherwise shown. I checked and your ancestor is not on this list. To make sure I have the following correct I checked my notes and the units were organized into Divisions based on the Congressional District they were from. At the start of the war the 3rd District/3rd Division was comprised of Putnam, Schuyler, Sullivan, Adair, Linn, Macon, Chariton, Randolph, Howard and Boone Counties; the Commander was John B. Clark, Sr. My notes also show there were seven counties of MSG from Schuyler Co. Many in Wm. Dunn's Co. of the First NE Mo. who became part of Porter's men. (Dunn was a rather controversial figure, but, certainly played a role.) Therefore, my list of Capt. Flood's group would certainly be incomplete and your ancestor may well be out there on another list somewhere. Jim Magee is probably the best source for info. regarding the MSG, and there are many more knowledgeable individuals about this subject than I, but, I am happy to check further and share what info. I have and to help in any way. Good hunting.