The Carricks' third imaginative picture book involving the most popular of subjects. ""Long ago, when the Old West was new,"" Professor Potts, his wife, and their son interrupted a transcontinental train journey to unearth some large, unusual bones with the help of the family dog. Back East, the Professor tries various ways of putting them together; but though he achieves forms similar to those of triceratops, tyrannosaurus rex, and ""brontosaurus,"" there are always extra parts. Satisfied at last, he asks his wife to manufacture a skin, which she gladly does--using several giddy fabrics--so that when he finally unveils his ""tribrontosaurns rex,"" it is a truly amazing patchwork creation. This amusing flight of fancy is based on a germ of truth: early reconstructions often were made up of parts of more than one species (brontosaurus has only recently been discovered to be such a creation). Meanwhile, Donald Carrick's illustrations here are as lovely as watercolors--vividly evocative of the western landscape and the wonderfully cluttered scientist's workshop, and deliciously full of humor--as the Pottses puzzle over their bone supply and come up with their preposterous solution.