I agree with your assessment that this soldier isn't in an Infantry uniform, or the parts of the uniform described as being worn in the various accounts of the Home Guard. Since the link to the photo referenced doesn't zoom to examine detail I did a google image search of Indian Home Guard Civil War. The first image link that begins with a photo of an Osage has a gallery of images pertaining to the Trans-Mississippi: http://www.civilwarvirtualmuseum.org/1861-1862/native-americans-in-the-war/unidentified-federal-indian.php and a closer copy of this image, to help confirm your thoughts of Cavalry service. Unfortunately the tell tale emblem on his hat isn't visible enough. The Fort Scott site: http://www.nps.gov/fosc/historyculture/forgotten-warriors.htm adds to some confusion and lists this image as a Cavalry Soldier of the Indian Home Guard, like the Home Guard were Cavalry and not Mounted Infantry. Since this image is attributed to the collection of the Oklahoma Historical Society and the collection of the Wilson's Creek Battlefield, I'm unsure if either would have further info. such as name or tribal affiliation. As I'm looking at this photo a question arises, were the 14th armed with Remingtons? Enough of my ramblings, this is a Cavalry trooper.