1883.] OF THE ORDERS AND FAMILIES OF MAMMALIA. 179 



present divisions and terminology are no longer sufficient for the pur- 

 pose ; and some other method will have to be invented to show the 

 complex relationships existing between different animal forms when 

 viewed as a whole. The present time, preeminently distinguished 

 by the rapidly changing and advancing knowledge of extinct forms, 

 is scarcely one in which this can be done with any satisfactory re- 

 sult. All attempts to form a classification embracing even the 

 already known extinct species must be only of a very provisional and 

 temporary nature. There are, moreover, special difficulties in under- 

 taking this subject, to any one working on this side of the Atlantic. 

 It has often been remarked that the centre of gravity of the civili- 

 zation, arts, literature, and commerce of the world appears to be 

 shifting westward. This is certainly the case with palseontological 

 discovery. Our knowledge of the ancient condition of animal life 

 on the earth is being revolutionized by explorations in the so-called 

 *' New World." With regard to Mammals it is a curious fact, that 

 although research has been prosecuted in suitable localities in many 

 parts of Europe and Asia with considerable assiduity since the 

 beginning of the century, scarcely a single form has been found 

 which does not come within the limits of our actual ordinal groups, 

 or which would necessitate any important modification in a classifica- 

 tion based upon existing species. But in the New World, beginning 

 with the earliest known South- American extinct forms — the Toxodons, 

 Nesodons, Mesotheriums, &c., and passing to the still more wonderful 

 discoveries of the last ten years in the Western Territories of the United 

 States, we find ourselves in completely new realmsof life. We are all at 

 once confronted with numerous highly specialized forms, representing 

 apparently new ordinal groups, and still more numerous generalized 

 forms filling up the intervals, and breaking down the distinctions 

 between nearly all the best-established orders of higher placental 

 Mammals. With these I do not propose to deal in the present 

 communication. The very abundance of the material that has lately 

 come to hand is in itself an obstacle to drawing any satisfactory 

 generahzations from it, as it has not left leisure to the few who have 

 an opportunity of working at it to give such full and detailed 

 descriptions as are necessary for the guidance of those who have not 

 the advantage of examining the actual specimens. 



In systematic descriptions in books, in lists, and catalogues, and 

 in arranging collections, the objects dealt with must be placed in a 

 single linear series. But by no means whatever can such a series 

 be made to coincide with natural affinities. Tlie artificial character 

 of such an arrangement, the constant violation of all true relation- 

 ships, are the more painfully evident the greater the knowledge of 

 the real structure and affinities. But the necessity is obvious ; and 

 all that can be done is to make such an arrangement as little as 

 possible discordant with facts. In preparing the article "Mam- 

 malia " for the ninth edition of the ' Encyclopaedia Britannica,' such 

 a scheme had to be framed ; and the chief merit which I claim for it 

 is, that it departs as little as possible from the prevailing, or what 

 may be called traditional, sequences of arrangement. In the article, 



