8 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
Sevier fault as immediately responsible for the existing topography; the 
date of the fault must be sufficiently remote to allow much consequent 
and subsequent erosion after it occurred. 
Our route southward from Upper Kanab led us obliquely to the east 
of the Sevier fault line, which was not seen again until we turned west 
from Fredonia toward Pipe spring. The two following sections are de- 
voted to the notes made on the way there. 
THE Jurassic Sanpstones. — The cross-bedding of the Jurassic sand- 
stones exposed in the canyon of Kanab creek through the platform that 
fronts in the White cliffs, with an altitude of 6700 feet and a relief 
of a full thousand feet, was one of the most extraordinary structures 
seen during the summer. It has already been well described by 
Dutton (a, p. 150; b, p.35), but no one can pass its superb escarpment 
without wishing to tell something of its wonders. Characteristic views 
of its form and stratification are given in Plates 1 A, 1B, 2 A. The sand- 
stone is white, clean, and even-textured, with its oblique layers slanting 
at angles of from 20° to 26°, and descending to great sweeping curves 
that turn gently tangent to the floor on which they rest. Southward 
dips are more common than northward. We looked in vain for the 
completed summit curves of the oblique beds: none were to be seen. 
Each group of oblique layers is truncated by the removal of its upper 
part, and the lower part that remains is too incomplete to indicate with 
certainty the origin of this very remarkable formation. Whatever was 
the entire original form of the successive deposits which the oblique 
layers possessed immediately at the time of their accumulation, the upper 
part of each group seems in all cases to have been more or less deeply 
worn away before the next higher group of layers was deposited. The 
surfaces of truncation are of gentle declivity and curvature, and often 
seem nearly or quite horizontal. Some of the groups of oblique layers 
are still twenty, thirty, or more feet in thickness, the successive layers 
descending with remarkable regularity and parallelism from top to bottom. 
Other groups are reduced to hardly more than a few feet in thickness, 
although their horizontal extent often exceeds a hundred feet, thus sug- 
gesting that their present vertical measure is but a small fraction of their 
original height. We saw no rippling ; all the layers show very smooth 
lines on the outcrop face. The surfaces of truncation or local unconformity 
are marked by no uncertain deposits. The underlying layers are sharply 
cut off; the overlying layers rise gradually at first and then more steeply 
in long, sweeping curves. The sandstones seem to retain their cross- 
bedding up to the top of the cliffs, but in the upland north of the 
