THE 



AMEEICAN NATURALIST 



Vol. XLI December, 1907 No. 492 



PRELIMINARY NOTES ON SOME AMERICAN 

 CHALICOTHERES^ 



O. A. Peterson 



Comparatively little is known of the American forms of the 

 Chalicotherioidea; — an extinct family of mammals. Professors 

 Marsh,^ Cope/ Scott," and Osborn^ have from time to time pub- 

 lished brief accounts of the few fragments available, but nothing 

 comprehensive on the osteological structure of these unique ani- 

 mals has been accessible in America until quite recently. 



A short time ago Dr. W. J. Holland, Director of the Carnegie 

 Museum, gave the writer permission to submit to the Seventh 

 International Zoological Congress some brief notes on the splen- 

 didly preserved remains of Moroptw^ clatus INIarsh which were 

 secured by the Carnegie Museum from the Agate Spring Fossil 

 Quany in Sioux County, Neljraska. 



This important fossil quarry has yielded much material which is 

 now being prepared for study and publication. The quarry is 

 located in the valley of the Niobrara River in the Lower Harrison 

 horizon, and was evidently the bed of a stream, or perhaps the shore 

 of a small lake, during a portion of the ]\Iiocene time. The bones 

 were imbedded in a comparatively thin stratum of soft sandstone 

 which vas quarried out in large blocks. These were properly 



.^ Am. Jour. S.'ion.r, \ ol. XIW pp. IM 'irA, 1877. 

 ^American xXaturalist. \ Will, pi). 149-151, 1889. 



* American Nutur;,li<t. \ ol. XW 11. pp. 659-662. 1893. 



• Bull. Mus. Comp. VamA.. \o\. XX. i)p. 99-100, 1890. 



733 



