Ay eas BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 
West of Leeds and Harrisburg, at the southwestern base of the Pine 
Valley mountains, we have more marked remnants of the ancient topog- 
raphy in the form of long, gently sloping grade plains which are now 
mere strips stretching forward from the edge of the mountains. As one 
looks westward from Leeds, most of the view consists of naked hills with 
steep rocky sides of red, white, and brown sandstone. The harder layers 
stand up as cuesta-like ridges across the spurs which run out from the 
mountains toward which the strata dip; the softer ones form depressions 
separating these lines of elongated knobs, which, if united, would form 
cuestas. Both alike are almost bare of soil, aud support scarcely any 
vegetation except sagebrush and cactus and a little desert grass. Here 
and there, however, almost parallel to the present valley floors although 
several hundred feet above them, run long but broken lines of green, 
sloping gently from the mountains toward the river. They seem to be 
remnants of the former mature topography, not yet consumed by the 
revived erosion of the canyon cycle. Their verdure is in part merely 
apparent, because they are level and hence are seen foreshortened, while 
in part it is real because of the fact that they are well graded and hence 
have a depth of soil sufficient to support a growth of juniper trees. 
Other examples of a similar kind are found near St. George and along 
the South Fork of Ash creek near Bellevue. In the former place, which 
will be described at some length below, the erosion of the present cycle 
has gone so far that but little remains of the old topography except 
those portions that are buried under lava flows. These form mesas, and 
along their borders are exposed most excellent sections of the ancient 
topography, showing conclusively its mature character. The South Fork 
locality, on the other hand, lies near the headwaters of the stream, and 
in a place where lava flows a little farther down Ash creek have pre- 
vented deep erosion. Accordingly here the features of the former cycle 
are well preserved. They take the form of broad well-graded slopes 
lying between sharply incised canyons of no great depth which represent 
the erosion of the present cycle. 
Turning now to some places at a greater distance from the Hurricane 
fault, but still belonging to the downthrown St. George block west of the 
displacement, we find that near Black Rock, forty-five miles southwest of 
Toquerville, the broad flat notch at the divide between the Grand wash 
and the Virgin displays for the most part a mature type of topography, 
even where there is an ascent of a thousand feet to the Shivwits plateau 
on the east and to the Virgin mountains on the west. Twenty-five 
miles down the Grand wash the main features of the topography are 
