146 



SCIENCE. 



[N. S. Vol. XII. No. 291. 



are some others which are used with reference 

 to the same subject. 



Charles A. White. 

 Smithsonian Institution, 

 July 12, 1900. 



initiation of new elements in fossil 



FAUNAS. 



The constantly growing refinement in inves- 

 tigative method that is demanded by every 

 branch of geological science has caused even 

 the most familiar phenomena to be examined 

 from new view-points. In no department of 

 geology has this change of position been more 

 marked than in paleontology. In problems of 

 geological correlation and comparative chronol" 

 ogy the individual species of fossils have come 

 to be considered more from the standpoint of 

 dependent components of complex faunas than 

 as mere isolated accidental factors. 



With this closer study of organic remains and 

 in their consideration broadly as distinctive as- 

 semblages or faunas, there has arisen a ten- 

 dency on the part of paleontologists to give new 

 meanings to old conceptions. Conspicuous 

 among examples of this sort is a decided prone- 

 ness to push backward the geological time di- 

 visions. 



As an illustration, the appearance of an Or- 

 dovician type among fossils occurring in recog- 

 nized Cambrian is pointed out as profoundly 

 significant. The occurrence of several such 

 younger factors among older ones has given 

 grounds for proposing to lower the basal line of 

 the newer terrane notwithstanding the great 

 preponderance of the older forms of life. 



The initial appearance of younger or newer 

 faunal elements is no doubt highly significant, 

 but it can hardly have the transcendent im- 

 portance often ascribed to it. The importance 

 of all such events is fully recognized. When, 

 however, it comes to making one or a few fac- 

 tors of this kind overbalance predominating 

 older elements some caution is necessary. 



We can hardly consider a new faunal age to 

 begin with every initial introduction of a new 

 faunal element. Faunas have their beginnings 

 far down in depths of older faunas. They ex- 

 pand, displace the older elements and culmi- 

 nate. They decline and fade away far up 



among still newer faunas. We have analogous 

 examples in the progress of nations. The initi- 

 ation of a new element does not indicate a new 

 dynasty. A new political movement has its 

 birth amid a multitude of conflicting elements. 

 It may grow in importance and finally displace 

 the existing government. Only when it has 

 overcome the older^ ruling powers is a new 

 regime inaugurated. Not until then does the 

 nation acquire a new name. There are long 

 steps between the initiation of a new element 

 and the initiation of a new regime. 



So, also, the relative geological ages of rock 

 sections more or less remote from one another 

 is now capable of being determined with great 

 accuracy by methods other than the use of fos- 

 sils. Modern stratigraphy rests upon grounds 

 wholly different from what it did even a few 

 years ago. The exact position of a terrane in 

 the general geological column is now not so im- 

 portant as the relative local position with ref- 

 erence to known associated formations. Faunal 

 age has ceased to be any longer a vital consid- 

 eration to the geologist. When he has found 

 out what are the geological units, or terranes, 

 and their relations to one another, he cares 

 little or nothing about what biotic age is as- 

 signed. He has in his possession the skeleton 

 frame work which he can, at his leisure, clothe 

 with flesh and blood. No subsequent finding 

 of ' Devonian ' fossils in one part, ' Carbonifer- 

 ous ' forms in another, or even ' Tertiary ' spe- 

 cies underneath all will change the ascertained 

 relative position of his units. The disputes of 

 ' exact geological age ' according to a standard 

 that he no longer recognizes as infallible or es- 

 sential, concern him little. If the question of 

 ' geological age ' or rather ' biotic age ' can be 

 settled even approximately satisfactory to all so 

 much the better. If not, his stratigraphic work 

 can go on without interruption. Questions as 

 to age according to this criterion or that, are 

 left for those who have more time than he to 

 answer them. Chaeles R. Keyes. 



rapid changes in the structure of the 



CORONA. 



To THE Editor of Science : The question 

 as to whether rapid changes take place in the 

 structure of the corona is an interesting one. 



