4 Bulletin American Museum of Natural History. [\'ol. XXVII. 



at the suggestion of Professor F. J. E. Woodljridge of Columbia University, 

 devoted attention to a study of Descartes and to the principles of the induc- 

 tive process, and also had the pleasure of acquiring from Professor Wood- 

 hridge's lectures a certain point of view regarding the nature of evolution 

 which has been of much service in the following studies. The author's ideas 

 about ordinal classification were developed partly as a by-product of studies 

 in ichthyology under his honored friend and instructor Professor Bashford 

 Dean, who for many years past has most heartily aided him in manifold 

 ways. The resulting arrangement of the Teleostomous fishes,^ which was 

 developed from the widely divergent systems of the leading authorities, 

 led to a general conception of the history, methods and limitations of or- 

 dinal and superordinal classification which has been a]iplied to some ex- 

 tent in the present work. 



To Professor Max Weber's epoch-making work 'Die Saugetiere' (1904) 

 reference is constantly made in the following pages; and to that work more 

 than any other will be due a synthetic view of the Mammalia, in which the 

 data of systematic mammalogy, of comparative anatomy, and embryology 

 shall ultimately be integrated with the data of paLneontology, to the great 

 advantage of each of these now more or less independent lines of study. 



The long series of publications by Professor Osborn naturally enters 

 very frequently into the consideration of the problems touched upon below. 

 The fruitful ideas of general and local adaptive radiation, of parallel, diver- 

 gent, and convergent evolution, of homology, homoplasy, and rectigradations, 

 of polyphyletic evolution, etc., which have gained widespread acceptance, 

 have been of constant service to the writer, and the same is true of that 

 author's work on Tertiary mammal horizons, on the evolution of the teeth, 

 on the foot structure of Ungulates, and on the phylogeny of the titanotheres, 

 rhinoceroses, horses, amblyjoods, etc. 



It is also pleasant to acknowledge indebtedness to several other friends 

 for favors extended during the preparation of this work : to Dr. T. S. Palmer, 

 author of the 'Index Generum Mammalium,' for reading the first rough 

 draught of Part I and offering many very helpful criticisms and suggestions; 

 to Dr. Theodore Gill for assistance in finding certain works and for his nu- 

 merous published contrilnitions to the history of zoology; to Charles Gregory, 

 Esq., for the gift of the valuable work of Perrault (1731) described on pages 

 39, 40; to Mr. C. Forster Cooper, M. A., of Trinity College, Cambridge, 

 for very kindly reading the manuscript of Part II with great care and making 

 many helpful criticisms; finally to Dr. J. A. Allen, the honored editor of 

 the Bulletin and Memoirs of the American Museum of Natural History. 



1 Ann. N. Y. Acad. Sci., XVII, 1907, pp. 437-508. 



