HARDWICKE'S SCIENCE-GOSSIP. 



49 



THE HORNED HOOFED MAMMALS OF THE EOCENE 



PERIOD IN AMERICA. 



By AGNES CRANE. 



{Continued from p. 40.] 



j«1^w^^ HIRTV species of 

 Dinocerata, all 

 from the middle 

 Eocene deposits of 

 Wyoming, the only 

 locality in which 

 their remain have 

 been hitherto foun d , 

 either in the New 

 or the Old World,* 

 are fully described 

 and illustrated in 

 the present memoir. 

 They are all re- 

 ferred by Marsh to 

 three well-marked 

 genera, and of two, 

 Dinoceras and Ti- 

 noceras, he has 

 been able to give 

 The least known is the 

 Uintatherium of Leidy (Uintat, Indian name, and 

 6-qpiov, a wild beast). This, the smallest and the 

 most generalised form, occurs in the lowest beds of 

 the series. Dinoceras, Marsh, in the succeeding de- 

 posits, and Tinoceras (tiVcc, to tear, itepas, horn), 

 the most specialised form in the upper beds only. 

 All the dinocerata are shown to have the smallest 

 proportionate brain, with the most reptilian characters 

 of any known mammalian animals. Of ponderous 

 build, and slow in movement, but well armed, they 

 held their own while the conditions of life were 

 suitable, but could not battle with changed or adverse 

 surroundings. Thus their total disappearance, leav- 

 ing no immediate successors, Professor Marsh holds 

 to be fully accounted for by the elevation and drainage 

 of the lake basin, and subsequent drying up of the 

 swampy soil into hard ground on which they were 

 ill-adapted for progression. 



* Unless the Coryphodoatidae be considered Dinocerata. 



No. 255. — March 1886. 



complete restorations. 



Such was the life history of the extinct Eocene 

 dinocerata as revealed by Marsh in a magnificent 

 monograph which adds to the high renown of its 

 author, and is in every way creditable to the Geo- 

 logical Survey of the United States Government, long 

 famed for the value and surprising excellence of its 

 publications. Here we may briefly refer to another 

 publication just to hand, and representing the topo- 

 graphical branch of the same Survey, i.e. the new 

 sheet of " the geological map of the United States, 

 exhibiting the present status of knowledge relating to 

 the areal distribution of geological groups, a prelimi- 

 nary compilation, by W. J. McGee, 1884." This 

 embodies the published results of the different inde- 

 pendent State surveys, with those of careful re-study 

 of difficult points in the field, and as all doubtful 

 and uncertain matter is excluded, it may be considered 

 accurate so far as it goes. It is a work of which 

 Americans may well be justly proud, as showing the 

 immense efforts that have been made in grappling with 

 so vast a portion of the New World, in tracing the 

 outcrops of the great geological formations, and 

 defining their exact boundaries. For the geological 

 structure of rather more than four-sixths of the 

 United States has been thus accurately determined, 

 that is to say, all that portion stretching eastward 

 from the outfall of the Colorado river to the Atlantic 

 seaboard, and northwards from the Gulf of Mexico 

 to the forty-ninth parallel. Washington Territory, 

 Idaho, Oregon, U. and L. California, three-fourths 

 of New Mexico, and half of Nevada and Arizona, 

 with a small extreme S.W. portion of the empire 

 state of Texas are left uncoloured. But it must not 

 hence be inferred that nothing is known of the geology 

 of the Pacific coast. The investigations of Cope in 

 Oregon have revealed the presence there of miocene 

 deposits, and the independent State surveys of 

 California have accumulated much published and 

 unpublished material ; but this knowledge was not 

 sufficiently defined as regards limit of outcrops, and 



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