I am having trouble using the internet at this time but if one suspect's the beardless man of not being Gen. Ben McCulloch a good guess would require ruling out his brother, General Henry Eustace MuCulloch.

I'm using Ezra Warner's "General in Gray" and the two Generals are shown as looking an awfully lot alike each other except for the age difference (Eustace McColloch is pictured much older) and the fact Eustace is clean shaven. Whether or not that is a clue I can't say.