214 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
Tue Kanab Periop. In the regions far from the coast uniform con- 
ditions may have prevailed unbroken to the end of the Mesozoic. Near 
the shore, however, there was a break at the beginning of the Kanab 
period, as is shown near Toquerville by a bench-making layer of mauve 
sandstone one hundred feet thick in which the strata are strongly cross- 
bedded on a large scale. Throughout the overlying massive red sand- 
stone there is. an alternation of cross-bedded and _ horizontal strata, 
suggesting that during the long period of their formation there was a 
constant change of conditions. Although conditions of uneven deposi- 
' tion, like those which will be discussed in connection with the succeeding 
Colob formation, prevailed to a great extent and caused the cross-bedding, 
there seem to have been shorter times of even deposition like that of the 
Painted Desert period. 
Tar Cotos Periop. The Colob period, which follows the indetermi- 
nate Kanab, seems to be unique in geological history. Its strata, like 
those of the Shinarump, have been tacitly assumed to be of marine 
origin, and there has been little or no attempt to account for their © 
peculiar features. A study of these leads us to query whether this too 
may not be of continental origin. The Shinarump suggests a piedmont 
deposit formed during a time when many streams flowed out upon a 
coastal plain, and when the climate was moist enough to allow the 
growth of forests upon the lowlands. The Colob suggests a piedmont 
deposit formed during a time when the climate had become so dry that 
a great desert drifted its sands in huge dunes over an area as large as 
the state of Indiana. 
In the lofty plateau east and northeast of Toquerville the strata are 
but slightly tilted, and fine vertical sections are exposed in the steep 
walls of numerous narrow canyons. The best example of these that we 
saw is Kanab canyon, although the same features are almost as well 
displayed in several other places. Here the white sandstone is cross- 
bedded on a scale so large that a single layer attains a thickness of from 
five to fifty feet. Most of these layers have a very persistent and uni- 
form dip of twenty or twenty-five degrees varying in direction from 
southeast to southwest. Other directions of dip are seen, but they 
seem to be rarer and less steep. The top of every inclined bed is 
smoothly truncated by what at first seems to be a horizontal layer, from 
which rises a new cross-bedded series. It is remarkable, however, that 
in every case where the strata were closely examined this apparently 
horizontal layer proved to consist of the lower portions of the overlying 
inclined strata, which, as they approach the underlying plane of trunca- 
