Columbus, Ohio, 3farch 7, 1876. 

 Dear Sir: I send you herewith, on the fossil floras of the western 

 Territories, a record of the progress and discoveries in this section of 

 the jSTorth American natural history, since the publication of the last 

 annual report for 1873. 



The memoir is divided into two parts. The first refers again to the 

 evidence afforded by fossil plants to the age of the lignitic formations; 

 and describes the species not yet known from former communications. 

 The second critically reviews the Cretaceous flora of the Dakota group, 

 and describes also, with figures, the new materials obtained from this 

 remarkable formation. This revision was demanded not only by the im- 

 portant discoveries'which have enriched this flora, but especially by the 

 kind criticisms of European authors and the great interest with which 

 .the publication of the (Cretaceous flora has been received by geologists. 

 Very respectfully, yours, 



L. LESQUEREUX. 

 Prof. F. Y. Hayden, 



United States Geologist, WasliiTigton. 



18 H 



273 



