210 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
strata were flexed and plicated to an extreme degree, while those of 
the west are for the most part calm and even. Only in the vicinity 
of the mountains and shore lines do we find them much disturbed ” 
(a, p. 13). All the Mesozoic beds are remarkably uniform in thickness, 
lithological character, and minute structure such as cross-bedding over 
the whole great plateau area from the Pine Valley mountains to Western 
Colorado, and from the middle of Arizona to the southern margin of the 
Uintas. They are thicker on the edges near the old shore line, and 
diminish quite rapidly for two or three leagues, but after that the 
diminution is very slow (c, pp. 47, 48, 208). 
During the beginning of the Tertiary marine deposition continued in 
many places, but soon the region was elevated and vast lakes were 
formed. Sedimentation continued in these to an enormous extent, al- 
though gradually the lakes were filled or desiccated, those at the 
extreme south becoming dry first and those at the north near the 
Uinta mountains persisting longest (a, pp. 216-219). 
The main outlines of this history, as thus summarized from Dutton’s 
account, have been placed beyond a doubt by the painstaking work of 
the earlier observers. When they wrote their reports geologists were 
only beginning to understand that it is possible for thick and extensive 
deposits to be laid down on land without the intervention of large bodies 
of water. Accordingly they assumed that all the Paleozoic and Meso- 
zoic strata of the Plateau province were marine, and the Tertiary strata 
lacustrine. Professor Davis (a, p. 373) has raised the question whether 
these may not be only in part lacustrine, while perhaps a larger part 
were deposited subaerially in the form of fluviatile fans, deltas, and 
flood plains. As Tertiary strata occur but scantily in the Toquerville 
region and are only of Eocene age, their history will not be further con- 
sidered.. Nor will Paleozoic history be considered, since we have no 
data beyond those which were available to Dutton. Although the 
cross-bedded sandstones in the lower part of the Aubrey remind us of 
the need for further study, there is no reason for doubting the main 
conclusion that most of the Devonian and Carboniferous strata were de- 
posited in a sea of moderate depth. The Moencopie series was probably 
laid down in a shallow sea where estuarine conditions may possibly have 
prevailed, as is indicated by the intercalated layers of gypsum, and the 
almost total lack of fossils in strata admirably adapted to their preserva- 
tion had they existed. 
Tue Sainarume Lanp. At the close of the Permian, or Moencopie, 
the sea retired (Dutton, c, p. 211) and the greater part of the Plateau 
sini eee 
tn Spo A A A Se ALONE 
Gee oi barre re 
yt to oteenreto gp eins eye te 
ae a ee ee a 
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