SUMMARY 



341 



able on the iiortliei'ii e.xteiisioii of the Morrison/^' This is in a iiieasiii-e 

 substantiated l)y the 'i') species that raii.^e ii|)\vai'<l iiil<> the Alhian ( I'a- 

 tapsco formation) of Man hind and \'ii',i;inia. 



Summary 



1. Both the W'eahh'ii and Potomac thuas, on ihe ground ol' the struc- 

 tural relations of the containing- \)rt\i^ and on the ground of their syn- 

 ehroneity with floras of othei' areas of a known st rat inrajihic position, as 

 determined by invertebrate ])aleontolo<iy, are refei'red to the Lower Cre- 

 taceous. 



2. The eastern faunas, considered as of the same age as the Morrison 

 by Marsh, Hatcher, and Lull, are undei-lain by from '^OO to 400 feet of 

 Cretaceous sediments containing- a Lower Cretaceous flora which in the 

 l^ocky Mountain ])ro\ince is first found ii! the Kootenai formation, whicli 

 is partially equi\alcnt to or at most coufoi inable on the ]\Iorrison. 



3. The Kootenai tloj-a appears to be most similar t(j the Konie floi'a of 

 Greenland, which is ]iot oldei' than Barremian and possibly somewhat 

 younger (perhaps Aptian). 



i. If this correlation is correct, then at least some of the Morrison must 

 be of Lower Ci'efaceous age. 



In conclusion, it seems to me that in discussions of this sort we should 

 not lose sight of the fact that human taxonomies ha\e no objective ex- 

 istence. 'J'hose of geology are at best units of a filing system, hy means 

 of which we arrange our knowledge of earth history. Tt would undoubt- 

 edly be less troublesome if we could interpret this history in the way that 

 Cuvier did. 



As it is today, while we re])udiate Cuvier's catast I'ophics and I'cxdlu- 

 lions. all oui- ai'guments ai'e tinged with the ancient heresy that Moras 

 and, faunas developed almost intact up to a certain time, when, presto 

 change! — Jurassic inxcrtebi-ates were re|)laced by Cretaceous inveite- 

 brates. The last dinosaui- hd't the world as precipitately as the last Moor 

 quitted (irenada. oi' the Angiosperms sprang into existence like T'allas 

 Athene. 



It is inconceivable to me that faunas or floras have even undeimuie 

 anything ol her than an orderly e\olution, except where i-elati\-ely sudden 

 changes (if cn\ ir(;iiment caused a \'ery local re|)lacement of the kind the 

 ])aleontologist assumes (not theoretically, but in practice) was on a uni- 

 versal scale. Imcii llie laltci-h famed method (d' diasl i-oi)iiism is based 



'• C. A. Fisher: Kconoriiical (ieology, vol. ill, 1908, p. 77. Bull. U. S. Geol. Survey, 

 No. 356. 



