NOTES ON THE INVERTEBRATE FAUNA OF THE DAKOTA 

 FORMATION, WITH DESCRIPTIONS OF NEW MOLLUSC AN 

 FORMS. 



[With plate VIII. ] 



By Charles A. White, 



Honorari/ Curator of Mesozoic Invertebrate Fo.inUs. 



Although the Dakota formation is of great geo!nrai)liical extent, 

 and, stratiftrapliically, one of the most clearly defined of the divisions of 

 the North American Upper Cretaceous, comparatively little is known 

 of its contemporary tauna. Of its Hora, however, which is a great and 

 varied one, much more is known, and remains of its numerous specific 

 forms are generally used in the paleontological characterization of the 

 formation. Those remains consist largely of augiospermous leaves, 

 and a greater or less number of species have been found in all the dis- 

 tricts where the formation has been recognized.* 



The discovery of vertebrate remains in Dakota strata was, some 

 years ago, publically announced, but it has since been ascertained that 

 they came from the underlying Jurassic strata. It is, therefore, not 

 yet certain that remains of land animals of any kind Inive been found 

 within the proper limits of this formation, which fact, in view of the 

 evidence we have of the contemporaneous prevalence of a great and 

 varied land flora, is quite remarkable. 



Notwithstanding the great geographical extent of the Dakota forma- 

 tion, only three discoveries of invertebrate remains have, so far as I am 

 aware, been made in its strata. The first of these discoveries was 

 made by Dr. F. V. Hayden in the valley of the Missouri River, at a 

 few localities within a small district which embraces the mouth of the 

 Big Sioux River. The second discovery was made by Prof. B. F. 

 Mudge in Saline County, Kansas, and the third by Prof. L. E. Hicks in 

 Jefferson County, Nebraska. 



Those which were discovered by Dr. Hayden are described and 

 figured by Mr. F. B. Meek in Volume ix of the U. S. Geological Survey 



*See The Flora of the Dakota Group, by Leo Lestinereiix; Monog. xvii, U. S. 

 Geological Survey. Washiugton: Government Priutiug Office, 1891. This is a post- 

 humous publication, edited by Prof. F. H. Knowlton. 



Proceedings jSTational Muaeum, Vol. XVII— No. 995. 



131 



