( 



MEDIEVAL OR MESOZOIC TIMES. 201 



Cretaceous and Mesozoic times in the West. Clarence King, Le 

 Comte, Stevenson, Powell, Newberry and Cope, however, regard 

 the next group above (Laramie Group of King and Hayden), as the 

 ■closing member of the Cretaceous. It will, however, suit my present 

 plan best to consider the Laramie (also called by Hayden Lignitic 

 Group) as the transition group from the Cretaceous to the Tertiary. 



The vegetable remains found in the Fox Hills group still indicate 

 the presence of cycads, zamias, tree ferns and araucarian pines, but 

 in greatly diminishing proportionate numbers. There is already a 

 large admixture of more modern tree forms. 



Animal life was specially rich in molluscan forms, closely related 

 to that of the preceding group, or Fort Pierre fauna. Like the 

 latter, it contains the remains of many chambered shells, such as 

 baculites and scaphites, the latter being specially abundant and 

 beautiful. Xo more beautiful shell ever existed than Scaphites Con- 

 radi, which is found in these deposits. Other unrivaled shells and 

 bivalves were also abundant. Vertebrates were represented by nu- 

 merous fishes and some large reptiles, the commonest being in the 

 Fort Pierre group, Mosasaurus Missouriensis. Xo doubt the plains 

 of Nebraska, during this epoch, was the home of huge Dinosaurs 

 and reptilian birds, but their remains, under the geological circum- 

 stances of the times, could not be preserved to us. 



Laramie Group. 



This is the Lignitic group of Hayden, but changed to Laramie 

 by mutual agieement between Dr. Hayden and Clarence King. 

 Like the preceding, it is not exposed in Nebraska, but may be 

 present in the northwestern part of the State, underlying the Ter- 

 tiary. A line joining the Laramie on the Missouri and its eastern 

 exposures in Colorado, would pass across northwestern Xebraska. 

 As this grcup is known in numerous places to pass under the Mio- 

 cene, its presence in northwestern Xebraska in the same position 

 is not impossible. However that may be, it represents, even more 

 than the preceding, a very long epoch, and the history of our plains, 

 the greater part of which at least was, during its continuance, a 

 land surface, can only be surmised by studying the character of this 

 group, and the events which it represent--. 



It is the last of that series of groups, commencing with the Da- 

 kota, that are conformable through their united thickness of not 

 less than 12,000 feet in the Rocky Mountain region. Of these 

 12,000 feet of sediment, four-fifths are of sandy materials, more or 



