ACKNOWLEDGMENT 



The author wishes to acknowledge his obligation to the many 

 friends and co-workers who loaned or gave specimens needed for the 

 preparation of the illustrations in this book. 



While all of the illustrations are original and are prepared from 

 photographs by the author, it would not have been possible to carry 

 through this part of the work without the help of others. 



The late Dr. J. B. Smith gave freely many excellent specimens 

 from his collections. A great deal of valuable material was furnished 

 by Dr. E. P. Felt. Special acknowledgment is due also to Dr. L. 0. 

 Howard and his associates, Mr. A. L. Quaintance, Dr. F. H. Chitten- 

 den, Mr. W. D. Hunter, Mr. F. M. Webster, Mr. E. A. Schwarz, Dr. 

 A. D. Hopkins, Dr. H. G. Dyar, Mr. So A. Rohwer, and Mr. Otto 

 Heidemann. 



Similar generous courtesies were extended by Dr. W. E. Britton, 

 Mr. P. J. Parrott, Professor G. W. Herrick, Dr. S. A. Forbes, Pro- 

 fessor H. A. Gossard, Professor H. Osborn, Professor C. P. Gillette, 

 Dr. T, J. Headlee, Professor F. L. Washburn, Professor Wilmon 

 Newell, Professor R. H. Pettit, Dr. E. D. Ball, Mr. E. L. Worsham, 

 Dr. H. T. Fernald, Prof. Franklin Sherman, Jr., Dr. W. E. Hinds, 

 Professor H. Garman, Mr. Lawson Caesar, Professor T. B. Symons, 

 Mr. N. E. Shaw, Dr. E. G. Titus, Dr. Leonard Haseman, Dr. Edith 

 M. Patch, Prof. R. L. Webster, Mr. J. S. Houser, Prof. A. G. Ruggles, 

 Mr. C. R. Crosby, Mr. F. E. Brooks, Mr. Patricio Cardin, Mr. J. J. 

 Davis, Dr. H. J. FrankUn, and Mr. W. S. Abbott. 



Grateful acknowledgment is here made to the author's assistants. 

 Miss Cornelia F. Kephart and Mr. C. H. Hadley, Jr., for their invalu- 

 able and skillful help throughout the work of preparing both illustra- 

 tions and manuscript. 



