A NEW DESCRIPTION OF SANIWA ENSIDENS LEIDY, 



AN EXTINCT VAEANID LIZARD 



FROM WYOMING. 



By Charles W. Gilmore, 

 Associate Curator, Division of Paleontology, United States National Museum, 



INTRODUCTION. 



In 1870 Dr. F. V. Hayden discovered the fossil remains of an ex- 

 tinct lizard in the Bridger deposits, Eocene, in the vicinity of 

 Granger, Sweetwater County, Wyoming, which Dr. Joseph Leidy 

 briefly described ^ as Saniwa ensidens. 



The type specimen was deposited in the United States National 

 Museum, where it has remained in the same unprepared condition as 

 originally received 50 years ago. It was preserved in a considerable 

 number of blocks of ash-colored rock, the only evidence of the em- 

 bedded specimen being two vertebrae, which had been uncovered, and 

 the numerous bones which protruded from the broken faces of the 

 rock. 



Recently this specimen has been fully prepared by Mr. N. H. Boss, 

 preparator in the Section of Vertebrate Paleontology, and under his 

 skillful manipulation all the contained bones have either been en- 

 tirely freed from the matrix or worked out in bold relief. This work 

 has resulted in uncovering many elements whose former existence 

 was unknown, and especially important was the discovery of a con- 

 siderable part of the vertebral column and the greater portion of the 

 skull and lower jaws. 



Since paleontology as yet affords ver}- little information concern- 

 ing the evolution of the more specialized land lizards, the unusual 

 perfectness of the skeletal remains of the present specimen, coupled 

 with the fact that Saniwa ensidens was the A^ery first extinct lacer- 

 tilian lizard to be described from North America, it is of sufficient 

 interest to Avarrant a full and detailed description of the type 

 specimen. 



» Proc. Acad. Nat. Scl., Phila., 1870, p. 124. 



No. 2418-PROCEEDINGS U. S. NATIONAL MUSEUM. VOL. 60, ART. 23. 



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