I finally found the book, the library took all their over-sized books off the shelves where they'd previously taken up residence, & created a new, "Oversize" section. The book is "Fine Art Of The West", by Byron B. Price. And, I apparently had mixed 2 different saddles up in my mind. One was a Texas-style stock saddle, c. 1840-60, with horsehair anquera; from the Fleischer Collection, Scottsdale. The other being a Mexican saddle by Pedro Una & Son of Puebla, Mexico, with saddle bags trimmed with padded flower design. The type of anquera on the Texas-style saddle was called a "duck tail" anquera.