ACKNOWLEDGMENT
The Author desires to express his appreciation of the consultation and assistance of Professor Henry Fairfield Osborn, President of the American Museum of Natural History, New York City, and of the members of the Scientific Staff of the Museum, especially: Dr. Frederic A. Lucas, Director; Dr. W. D. Matthew, Curator of Vertebrate Paleontology; Mr. Walter Granger, Associate Curator of Vertebrate Paleontology (Mammals); and Mr. Barnum Brown, Associate Curator of Vertebrate Paleontology (Reptiles). The Author further wishes to express appreciation for the use of illustrations provided by the Museum, naming especially the restorations of Mr. Charles R. Knight.