INTRODUCTORY REMARKS. 

 Section of the White River group on White and Niobrara 'Rivers. 



L.xnr 



As no marine or brackish-water remains have been found in this group, 

 it is evidently an extensive fresh-water lacustrine deposit. The number of 

 vertebrate remains that have been found in it in the comparatively small 

 area occupied by the Bad Lands is truly surprising. Up to 1861, Dr. Leidy 

 had described more than sixty species of these fossils from this region, 

 belonging to the Ruminantia, Multungula, Solidungula, Rodcntia, Carnivora, 

 and Chelonia; and Professor Marsh has since described a number of others. 

 The Molluscan remains, however, yet known from these beds make but a 

 small showing compared with the vertebrates, as we only know some five 

 or six species belonging to the genera Helix, Planorbis, Limntea, and P/ii/sa 

 (see plate 45). So far as yet known, vegetable remains seem to be very rare 

 in this group. 



Although the area of the Bad Lands proper is comparatively small, the 



