588 



SCIENCE. 



[N. S. Vol. VII. No. 174, 



cisive evidence tliat the pes of Coryphoclon 

 was intermediate between the nearly planti- 

 grade Pantolambda and the sub- digitigrade 

 Uintatherium. 



In general CorypJwdon had a very short 

 back and short, spreading limbs, with a 

 very clumsy, shuffling gait. 



Henry F. Osboen. 



TEE 3IYTH OF THE OZABK ISLE. 



The Ozark uplift, which occupies neai'ly 

 all of south Missouri and northwestern Ar- 

 kansas, has long been known as the only 

 noteworthy elevation existing in the whole 

 continental interior plain. Geologically all 

 of this vast regioa, stretching out from the 

 Appalachians to the Eockies and from the 

 Great Lakes to the Gulf, is made up largely 

 of late Paleozoic or younger rocks, save in 

 one spot, the Ozarks. 



As a geographical feature the Ozark up- 

 lift is a great, broad dome. Its general sur- 

 face still preserves the outlines of the great 

 peneplain that existed in the region before 

 the country was affected by mountain-mak- 

 ing forces and bowed up. The margins of 

 the elevation are marked approximately by 

 the Missouri river on the north, the Mis- 

 sissippi on the east, the Neosho on the 

 west and the Eed river. 



The geological structure of the uplift is 

 relatively simple. In the highest or central 

 part are the oldest rocks exposed in the 

 entire Mississippi basin. These ai-e the 

 Algonkian granites and porphyries, the 

 commonly called Archasan nucleus. Sur- 

 rounding these massive crystallines and 

 occupying nearly all of the central portions 

 of the dome are the Cambrian and Silurian 

 dolomites, the so-called great magnesian 

 limestone series. Farther outward lie suc- 

 cessively the Devonian, Lower Carboniferous 

 and Coal Measures. The latter also form 

 the principal surface rocks of the surround- 

 ing plain, beyond the margins of the uplift. 

 Thus the great dome presents the oldest 



rocks in the central and highest parts, and 

 towards the margins and foot younger and 

 younger belts in concentric rings. 



This striking and peculiar arrangement 

 of the geological formations around the 

 Ozark dome has long attracted notice, and 

 it has always set forth as one of the direct 

 proofs that the uplift is very old and that 

 the region has remained practically un- 

 changed above sea-level since pre-Cambrian 

 times, forming in the midst of the broad 

 and shallow continental sea a large, ever 

 growing island around which sediments 

 were constantly laid down during all the 

 Paleozoic period. Starting with these prem- 

 ises there have been based recently a num- 

 ber of broad generalizations and rather fan- 

 tastic hypotheses regarding the deposition 

 and origin of various ores found in the re- 

 gion, the courses of Paleozoic ocean cur- 

 rents, the formation of unusually thick sedi- 

 ments of certain geological age, the distri- 

 bution of some ancient and peculiar faunas, 

 and even the isolated and independent de- 

 velopment of life in the region. These 

 various hypotheses are very attractive in 

 themselves. Based wholly on the assump- 

 tion of the existence of a large land area in 

 the middle of the continental sea, the colat- 

 eral evidence used in several of the argu- 

 ments are strangely corroborative. But 

 going back of the original proposition that 

 has been taken for granted and that has 

 served as the foundation for the several 

 hypotheses advanced, a question naturally 

 arises as to the real grounds for the premises 

 and for the assumed great antiquity of the 

 ' Ozark Isle.' 



If there is one thing that modern geogra- 

 phy teaches before all else in regard to the 

 existence of an elevated land area, such as is 

 claimed for the Ozark region during all the 

 long span from the pre-Cambrian to the 

 present, it is that it would have been long 

 since worn down to a low-lying plain of 

 faint relief, indistinguishable from the vast 



