251 
companied by a ‘descriptive pamphlet in which the characters, 
especially the microscopic ones, will be fully set forth. The fossil 
wood illustrates well the replacement of organic structure by 
silica, and in preparing the figures and descriptions for the Study 
Series it was found that it represented an apparently undescribed 
species of tree, and it has been thought desirable to publish a 
Proper diagnosis in advance of the distribution of the specimens. 
This silicified wood was collected in September, 1891, in the 
Upper Galletin Basin, Montana, just outside of the Yellowstone 
National Park. The trunk which afforded the specimens was an 
upright one, about eight feet in height and four feet in diameter, 
and, as subsequent study has shown, was admirably preserved. 
As the drawings show, its structure can be made out with almost 
as much satisfaction as though still living. 
The matrix in which the trunk was standing is the charac- 
teristic volcanic deposit of the region. It appears to be very 
Similar to, if not indeed identical with, that of the well known 
Fossil Forest on the Lamar River in the Yellowstone National | 
Park. Its geological age is therefore regarded as probably 
Miocene. 
PiTyOXYLON PEALEI n. sp. 
Annual ring very pronounced, 2-10 mm. broad; cells of sum- 
mer wood large, thin-walled; cells of fall wood thick, much com- 
Pressed ; cells of summer wood with a single series of large scat- 
tered punctations; medullary rays in a single series of two to 
about twenty long cells, marked radially with one to three small 
bordered pits in the width of each wood cell; resin tubes rather 
numerous, of large size. 
Cross Section—This section (Fig. 1) shows the late fall and 
early spring wood. The contrast in the size and thickness of the 
walls makes a very clearly demarked ring. This ring of growth 
was very broad, being in some cases fully 10 mm. The medullary 
tays show in this section also as long, slender cells. 
Radial Section—The fine state of preservation is well shown 
in this section (Figs. 2-4). The cells of the spring and summer 
wood are very broad and marked with a single series of large scat- 
tered bordered pits. The medullary rays are also prominent in 
this section. They are composed of very long cells, each of which 
is marked with usually two or three small oblong or nearly cir- 
cular bordered pits the width of each wood cell. — 
