204 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
the names “ Verkin,” “ Kanab,” and “ Colob” in place of Dutton’s “ Per- © 
mian,” ‘ Triassic,” and “Jurassic.” Since this paper was written, we 
have learned that Ward had already given the name “ Moencopie” to the 
‘* Permian” or “‘ Verkin”’ shales, and had used “ Painted Desert” in a 
somewhat indefinite way for shales of the “ Lower Triassic” or “ Lower 
Kanab.” In recognition of the priority of Ward’s names, we shall discard 
the term “ Verkin” in favor of ‘“ Moencopie,” and use “ Painted Desert ” 
for the soft sandy “ Triassic ” shales, restricting “‘ Kanab ” to the overlying 
hard red sandstone. ‘‘ Colob” will apply, as before, to the cross-bedded 
white sandstone, — the “Jurassic” of Dutton. 
The names Colob, Kanab, Painted Desert, Shinarump, Moencopie, and 
Aubrey apply to single groups of strata that are perfectly distinct from 
the other groups, not only in structure but also in outward appearance. 
Each formation has its characteristic color or group of colors, and under 
erosion assumes forms peculiar to itself. 
The colors of the rocks among the plateaus are a revelation to one 
who has seen only the neutral shades of the ledges in a region of granite 
gneisses and schists, or the soil-covered outcrops of a forested region. In 
the lofty buttes and bare rock-walls of the plateau country, one sees a 
most astonishing display of color, ranging from dull neutral shades of 
gray and brown on the one hand to delicate pink, rich chocolate, intense 
brick-red, or pure white, on the other. 
Wherever the color changes, in passing from one formation to the 
next, a complete change in the texture and structure of the rock results 
in an equally definite change in the shapes developed by erosion. A 
formation of soft shales may weather down into a long slope, passing 
below into a flat sandstone shelf that ends sharply in a sandstone cliff. 
Looking across the canyon of the Virgin river at Rockville, for example, 
the observer sees a terrace of brightly colored Moencopie shales beneath 
a dun-colored Shinarump cap, while beyond the hard platform of the 
latter, and above it, rise gigantic towers and cliffs of a sandstone that 
looks fairly red-hot. 
A few words about each of these formations will serve to give an idea 
as to the way each looks in the field. 
The Aubrey formation, in the Toquerville district, consists of a rather 
massive gray limestone, capped by a series of colored shales. The lime- 
stone resists erosion with much strength. Where it has been cut by 
the recent Hurricane fault, it stands up as a steep ragged wall. All 
along the face of the Hurricane its structure shows plainly, even at a , 
