This is an original illustration from Tik-Tok that was used as a header for Chapter 15, The Dragon Defies Danger. Quox is shooting flames from his mouth, after being threatened by the evil Nomes. This is another example of an illustration that was printed with an additional half tone in the book - in my opinion, to the detriment of the image. On the drawing, the background is colored a pale blue indicating the areas intended for shading, but I think the grey printing in the book results in a rather muddied image. An interesting side note - the ink blot that appears to the lower right of Quox in the drawing is present in early printings of the book, but disappeared in the 1960's white cover versions.
There are a number of dragons in the Oz books, from the underground den of Dragonettes, tied by their tails to their cavern walls, to the two-headed dragon in John R. Neill's own Oz stories. But my favorite will always be Quox!