We received the book Gail R. Thomas of Plano, Texas, on the ancestors of Lottie May Thomas. This section contains the direct relatives of Lottie May from Gail's posted Internet file, but his work is more extensive. We also found an on-line version of The History of Carrollton Manor, 1928, which was adjacent to the Thomas and Snauffer properties but both families are covered in the book. Gail Thomas mentions an additional book on the Thomas family written in the 1960's from which he gathered much material but found numerous errors. All of these works have differences with the census counts.
I think its fair to say that the Gail Thomas book is the most correct resource, and that resolving the issues between the books would be next to impossible. There were many Thomas's in Frederick County, Maryland; some English and some German, and many of the given names overlap. Known errors in the earlier works seem to come from confusion between individuals with the same given name and approximately the same date of birth.
From the books we can get a good picture of the English Thomas ancestors and descendants of Col. John Benjamin Thomas and the ancestors of his son Amos's wife Harriet Snouffer (parents of Lottie May Thomas).
Unless something else strikes an interest, we're probably done with this line.