50 PROCEEDIXGS OF THE BALTIMORE MEETIXG 



His Statement of the changes m fossil faunas in passing geographically 

 from place to place is as follows : 



"Upon tracing single species across these sections, it was learned that the 

 mutation of the species not only may be recognized on pa>:sing vertically up- 

 ward through a continuous section, but that the more direct line of succession 

 was often deflected laterally, so that the immediate successor of a particular 

 fauna of one section was found not directly above it in the same section, but 

 at a higher horizon in a section ten or twenty miles distant. This shifting of 

 faunas was taken as actual evidence of migration.'" - 



The correct correlation of the Catskill formation was an indirect result 

 of the application of the principles growing out of his method. He dem- 

 onstrated that instead of being Toimger than the Chemung the Catskill 

 formation was contemporaneous with it, the Catskill fauna living in 

 fresh or brackish water and the Chemung fauna in contemporaneous 

 marine waters. 



While examining the Devonian collections when on a visit to European 

 museums, his thorough acquaintance with the faunas of the Cayuga Lake 

 section enabled him to recognize the Tully limestone fauna (Devonian) 

 as the equivalent of the fauna of the Cuboides zone of Europe. He thus 

 established a definite line between the Eo and Meso-Devonian. He says: 



"The conclusions we draw from this study of the faunas of the Cuboides 

 zone and the Tully limestone are that within narrow limits, geologically speak- 

 ing, the point in the European time scale, represented by the beginning of the 

 deposition of the Cuboides Schichten of Aix La Chapelle. et cetera, is repre- 

 sented in the New York sections by the Tully limestone, and. second, that the 

 representative of the fauna of the Cuboides zone of Europe is seen in New 

 York not only in the Tully limestone, but in the shaly strata for several hun- 

 dred feet above. Therefore, if we wish to express precise correlation in our 

 classification of American rocks, the line between Middle and Upper Devonian 

 formations should be drawn at the base of the Tully limestone to correspond 

 with the usage of French. Belgian. German, and Russian geologists, who in- 

 clude Fi-asnein. Cuboides Schichten. and correlated zones in the Upper De- 

 vonian." ^ 



A consideration of the theories of evolution delighted him, and he loved 

 to speculate on the shades of meaning of terms used by Darwin, Huxley, 

 and others. The best statements of his own conclusions are to be found 

 in his Geological Biology (1895) ^nd in papers that grew out of the 

 writing of this book, which appeared in 1897 and 1898. 



Professor Williams '"was the author of upwards of 90 papers and books, 

 comprising nearly 3,000 pages, and of these about <'i.^ titles relate to 



- The scope of paleontolosry and its value to geologists. Am. Geol.. vol. x. 1892. pp. 

 148-169. 



2 Bull. Oeol. Soc. Am., vol. 1. 1890. pp. 481-500. 



