250 The American Geolo(j!st. April, i«95 
soraetliing over 600 feet. The beds tire composed of alternat- 
ing layers of a ver}'^ tine-grained cla}^ and sandstone, the latter 
passing at times into a hard conglomerate. Tiie deposits were 
divided Iw Hatcher (loc. cit. ) into two sets of beds, the Oreo- 
don and the Titanotheriuni beds, named from their charac- 
teristic fossils. Later (Bull. Am, Mus. Nat. Hist., vol. v, p. 
101) Wortman subdivided the upper into tiie Protoceras and 
Oreodon beds, so we have now : 
The Protoceras he<ls, 180 fi-ot, clays and coai'sc saiidslom'S. 
Tlie Oreodon beds, '^70 feet, mostly clays. 
The Titanotherium beds, 17.^ feet, clays and sandstones. 
It is in the two lower of these beds that the dikes occur. 
There are associated with the sandstones, veins of chalcedony, 
which may be either in connection with the sandstone or en- 
tirely separate, and the sandstc»ne may exist entirely free from 
the crystals of quartz. Speaking of these veins. Hatcher says 
(Am. Nat., March, 1898) : "In various portions of the Titan- 
otherium beds there are numerous vertical veins of chalce- 
dony running through the beds in everj'^ direction. These 
veins vary in thickness from that of a sheet of paper to about 
two inches. * * * Occasionally other minerals, as ordi- 
nary calcite and its common variety known as Iceland spar, 
are found in small cavities in these veins. * * * These 
veins occur onl}'^ in certain localities of limited area. Any 
single locality is never more than a few miles in extent." 
These observations relate only to the lowest bed and to the 
veins of chalcedony. During the stimmer of 1894 the writer 
was able, while in the bad lands, to make some observation on 
the occurrence in both the lower beds of not only the (chalce- 
dony veins but also the mud or sandstone dikes not mentioned 
by Hatcher. 
Let us consider first the dikes of soft sandstone or mud free 
from crystallized silica. The sandstone is not hard, but on 
the contrary is very soft and friable and seems in many cases 
to be little more than a mixture of sand and clay, sometimes 
passing into almost pure cla}'. They stand up from the sur- 
rounding cla3'-s but a few inches, in the greatest instance ob- 
served not to exceed six, and in weathering no blocks are 
formed, the disintegration is complete in the dike. The color 
of the intruded sandstone in the Oreodon beds is a light green 
