212 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
is confined so strictly to this particular horizon at the top of the Shina- 
rump. The land must have been forested both before and after the 
time represented by this formation, and there must have been winds 
and currents to carry the tree trunks. If the Shinarump is a continen- 
tal deposit, the difficulty disappears. On the first emergence of the 
land above sea-level vegetation would be lacking. Therefore the lower 
Shinarump would contain no fossil wood. Later the whole country 
would become forested and many trees would be buried under fluviatile 
deposits. Lastly, when the sea again encroached upon the land the 
whole forest would be buried in the new marine sediments, and we 
should find, as is the case at Toquerville, that this particular layer 
would be especially rich in fossil wood. 
One hundred and fifty miles southwest of the region that we have 
been discussing, Ward in his study of the district around the Little 
Colorado river has found similar and even more marked indications of 
land conditions. The Shinarump formation there increases to a thick- 
ness of sixteen hundred feet, and is characterized throughout by fossil 
wood and other signs of terrestrial ~igin (p. 405). The conglomerate 
“contains somewhat large, but always well-worn pebbles and cobbles 
derived from underlying formations ; still it rarely happens that this 
aspect of the beds forms the major part of them. In the first place the 
conglomerate tends to shade off into coarse gravels and then into true 
sandstones. These . . . are always more or less cross-bedded and usually 
exhibit lines of pebbles running through them in various directions. ... 
Although the sandstones proper generally occur lower down, still there 
is no uniformity in the arrangement, and sandstones are often found in 
the middle and conglomerates more rarely at the top.” In addition to 
these the Shinarump (p. 406) embraces other classes of beds, chiefly 
well-stratified thinnish sandstone shales which often thicken in short 
distances and become transformed into bluish-white marl. In the lower 
valley of the Little Colorado, where the Shinarump conglomerate is only 
three hundred feet thick, this feature is not prominent, but elsewhere, 
as in the Petrified Forest region where the formation attains a thickness 
of seven or eight hundred feet, “this tendency on the part of certain 
beds to become transformed into marls is the most marked feature of 
the formation. . . . These heavy marl beds . . . are interstratified be- 
tween conglomerates, coarse gravels, and cross-bedded sandstones. .. . 
These varying beds . . . often change the one into the other even at 
the same horizon within short distances” (p. 406). 
Overlying the conglomerate proper are the Le Roux or Belodont beds 
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