242 GEOLOGY. 



occurs. On the Niobrara, in the lower beds of the Pliocene, occur, 

 at rare intervals, palm-like leaf lemains, which probably belonged 

 to some species of sabal, though the remains were too indistinct to 

 identify. At the same horizon remains of fig leaves occur. There 

 occur, also, occasional remains of the Sweet Fern (Compfonia), 

 vSweet Gum, Locust (Robinid), Honey Locust (Gledilschid), Cassia, 

 Sumach (Rims), Walnut (Juglans), Tulip tree (Liriodendrori), Staff 

 tree {Celastrus), Cotton woods (Popdus), and Oaks. A petrified 

 oak log, from the Niobrara Pliocene, in the cabinet of the State 

 University, is remarkable for its beauty and the distinctness with 

 which its structure has been preserved. The cells and medullary 

 rays are as perfect as in a live oak of to-day. In Harlan County, 

 on the south side of the Republican River, occur masses of silicious 

 limestone that are filled with the petrified or semi-jDetrified seeds of 

 probably some species of Arrow-wood {Vibumam), which is a mem- 

 ber of our Honeysuckle family, which had its greatest develop- 

 ment in Tertiary times. A flora similar to this characterized 

 Europe during this epoch, but it disappeared at the end of the 

 Tertiary. Here, however, our conspicuous vegetable forms are yet 

 Tertiary in type, and almost in species. If Heer is correct, many 

 of our existing American species abounded already in Greenland, 

 Iceland and Spitzbergen in the middle Tertiary. So far, therefore, 

 as our flora is concerned, America, as has long since been remarked, 

 is the old world. 



Animal Life. — The turtle family was probably represented by 

 fewer species during the Pliocene than in the previous epoch. 

 Those that I have observed myself in the Niobrara Pliocene were 

 land tortoises, belonging to the genus Testudo. Their remains 

 were mixed with those of mammals. 



During this epoch the higher forms of vegetable life, and espe- 

 cially the mammalian type, had a remarkable development. They 

 must have been exceedingly abundant around the shores of the 

 great lake of the plains, as is evident from the vast numbers of 

 their remains. 



The birds were represented by an eagle (Aquila Daiianus) % and a 

 cormorant (Grits Haydeni), both found on the Loup, and described 

 by Marsh. The existence of the eagle implies the presence of 

 other species. And there can be no question that the happy physi- 

 cal conditions of those times were favorable to a great development 

 of bird life. 



