72 Saurians of the Dakota Beds of Colorado. (| February, 
Along both the eastern and western flanks of the Rocky 
mountains the Dakota beds form a distinctive feature of the land- 
scape. Their hardness has resisted the effects of erosion so that 
they remain prominent where other beds have been worn away. 
As all the earlier cretaceous strata lie tilted up against the great 
central axis, the harder ones form lines of hills or “ hog backs,” 
while parallel valleys mark the upturned edges of the softer ones. 
This role is played by formation No. 2, as has been often shown 
by Dr. Hayden. The side of the sandstone ridge next the moun- 
tains is steep, while the opposite one is sloping, and the summit is- 
is often a narrow ledge. Onthis elevated perch theancient Pueblos 
of New Mexico fixed their rock built houses, courting one peril to 
escape the greatest of all, the attacks of savage men. To-day these 
ruined abodes form the resting places of the geologist, the true 
lover ofyscenery, who climbs for birds-eye views of his favorite 
subjects, and for clews to many a knotty problem, 
As a shore and shallow water formation, the Dakota should 
enclose the remains of 
js Ss the plants and animals 
SSE | of the land. And plants 
have been found’ in 
abundance, and have 
| been the theme of an 
interesting volume of 
NS 
vertebrate remains 
were until recently un- 
what forms of animal 
life. ranged that unex- 
able continent, is 4 
Fig. 1—Cervical vertebra of Camarasaurus sur excursions among the 
premus. afrom above ; 4 from right side. The neural 
arch is mostly wantin These figures, like all the “hog backs” of Colo- 
others in this paper, are one-tenth natural siz rado and New Mexico; 
and many cliffs have been ‘eye and many fasts endured without | 
result in this direction. 
known. To ascertain — 
plored and unexplor- l 
problem that stimu- : 
lated the writer tomany — 
