Ilatictic0. 
The  general  features  and  ancient  Mammalia  of  the  Mauvaises  Terres  of 
Nebraska.  [Being  part  of  the  Report  of  D.  D.  Owen,  Esq.,  U.  S.  Geologist.] 
— After  leaving  the  locality  on  Sage  Creek,  [a  southern  branch  of  the 
Cheyenne,]  affording  the  above-mentioned  fossils,  [fossil  ammonites,  &c.  of 
the  Eocene  tertiary,]  crossing  that  stream,  and  proceeding  in  the  direction 
of  White  river,  about  twelve  or  fifteen  miles,  the  formation  of  the  Mauvaises 
Terres  proper  bursts  into  view,  disclosing,  as  here  depicted,  one  of  the  most 
extraordinary  and  picturesque  sights  than  can  be  found  in  the  whole  Mis- 
souri country. 
From  the  high  prairies,  that  rise  in  the  background,  by  a  series  of  ter- 
races or  benches,  toward  the  spurs  of  the  Rocky  Mountains,  the  traveller 
looks  down  into  an  extensive  valley,  that  may  be  said  to  constitute  a  world 
of  its  own,  and  which  appears  to  have  been  formed,  partly  by  an  extensive 
vertical  fault,  partly  by  the  long  continued  influence  of  the  scooping  action 
of  denudation. 
The  width  of  this  valley  may  be  about  thirty  miles,  and  its  whole  length 
about  ninety,  as  it  stretches  away  westwardly,  towards  the  base  of  the 
gloomy  and  dark  range  of  mountains  known  as  the  Black  Hills.  Its  mosfe 
depressed  portion,  three  hundred  feet  below  the  general  level  of  the  sur- 
rounding country,  is  clothed  with  scanty  grasses,  and  covered  by  a  soil 
similar  to  that  of  the  higher  ground. 
To  the  surrounding  country,  however,  the  Mauvaises  Terres  present  the 
most  striking  contrast.  From  the  uniform,  monotonous,  open  prairie,  the 
traveller  suddenly  descends  one  or  two  hundred  feet,  into  a  valley  that  looks 
as  if  it  had  sunk  away  from  the  surrounding  world ;  leaving  standing,  all 
over  it,  thousands  of  abrupt,  irregular,  prismatic,  and  columnar  masses., 
frequently  capped  with  irregular  pyramids,  and  stretching  up  to  a  height 
of  from  one  to  two  hundred  feet,  or  more. 
So  thickly  are  these  natural  towers  studded  over  the  surface  of  this  ex- 
traordinary region,  that  the  traveller  threads  his  way  through  deep,  con- 
fined, labyrinthine  passages,  not  unlike  the  narrow,  irregular  streets  and 
lanes  of  some  quaint  old  town  of  the  European  continent.  Viewed  in  the 
distance,  indeed,  these  rocky  piles,  in  their  endless  succession,  assume  the 
appearance  of  massive  artificial  structures,  decked  out  with  all  the  acces- 
sories of  buttress  and  turret,  arched  doorway  and  clustered  shaft,  pinnacle,, 
and  finial,  and  tapering  spire.  One  might  almost  imagine  oneself  approach- 
ing some  magnificent  city  of  the  dead,  where  the  labor  and  the  genius  of 
forgotten  nations  had  left  behind  them  a  multitude  of  monuments  of  ark 
and  skill. 
On  descending  from  the  heights,  however,  and  proceeding  to  thread  this 
vast  labyrinth,  and  inspect,  in  detail,  its  deep,  intricate  recesses,  the  reali- 
ties of  the  scene  soon  dissipate  the  delusions  of  the  distance.    The  castel 
