PROCEEDINGS OF THE UNITED STATES NATIONAL MUSEUM 



issued SWsK \ {^^m ^V ^^ 



SMITHSONIAN INSTITUTION 

 U. S. NATIONAL MUSEUM 



Vol. 91 Washington : 1941 No. 3124 



SOME LITTLE-KNOWN FOSSIL LIZARDS FROM THE 

 OLIGOCENE OF WYOMING 



Bv Charles W. Gilmore 



Among a small collection of Oligocene fossil remains acquired for 

 the United States National Museum in 1931, from George F. Stern- 

 berg, were two lizard specimens that contribute to a better understand- 

 ing of the cranial anatomy of the genera Aciprion and Exostinics. 

 These specimens were found in a small badland area of the Brule 

 formation that is bisected by U. S. Highway 20, about 8 miles east 

 of Douglas, Converse County, Wyo. A detailed description of them 

 follows. The illustrations were prepared by Sydney Prentice. 



Family IGUANIDAE 



Genus ACIPRION Cope 



ACIPRION FORMOSUM Cope 



Figures 30, 31 



An almost complete skull with both dentaries (U.S.N.M. No. 16566) 

 of Aciprion formosum Cope gives for the first time a comprehensive 

 knowledge of the cranium in this little-known genus and species. 



Skull. — The skull is complete except for part of the right jugal 

 and fragments of the squamosal of the same side. The anterior 

 half of the palate has been disari'anged and some of the elements 

 are missing. The lower jaws both lack their posterior portions. 



Most of the sutural contacts are discernible and so make it possible 

 clearly to depict the cranial details as shown in the illustrations. In 



406806—41 71 



