326 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
fied wood is retained. Over the surface of the trunk are a number of 
scars. The smaller of these would naturally be interpreted as either 
the cicatrices of possibly Araucarian leaves or perhaps as the rootlet 
scars of a Stigmarian root, if it were conceded that this genus were 
present so late as the Arizona Triassic. Investigation showed that 
neither of the more obvious interpretations of the smaller superficial 
scars could be adopted. Two larger scars appear, one in the middle 
line and another to the right of it. In the light of subsequent descrip- 
tion of the internal structure, it is clear that these are the broken bases 
of branches of the main axis. In Fig. 2 (PI. 31) is shown the opposite 
side of the same slightly flattened trunk. Part of the surface is ob- 
scured by the label of the Geological Museum, but enough is left clear 
to show that this surface presents a close similarity to that shown in 
Fig. 1. A little to the left of the middle line below, is seen a third 
larger scar, representing the broken base of a ramification. With 
some clearness on the right and left above may be seen, in longitudinal 
aspect, the organs which are responsible for the rounded scars in the 
middle line. The appearance thus presented indicates that a con- 
siderable amoimt of the surface of the trunk has been removed either 
previous to fossilization or more recently as a consequence of the 
weathering of the petrified trunk. By regarding the smaller scars 
shown in Figs. 1 and 2 with a pocket lens, it may be made out that they 
are multiple in their nature in some instances and represent a large 
main scar accompanied by one or more smaller scars. This can be 
made out with special clearness in the upper median region of Fig. 2. 
Fig. 3 represents the natural weathered end of the trunk shown in 
the two foregoing figures. The process of weathering has etched out 
aduiiral)ly the annual rings, so that they appear much more distinctly 
than they do even in microscopic sections of the better preserved 
parts of the trunk. By examination of the rings with a lens it may be 
readily determined that the trunk was ap})roximately half a century in 
age, when the tree was fossilized, if all the annual increments of growth 
are represented, which seems probable. It is possible to make out 
that some of the original layers of the wood are missing on the flattened 
surfaces of the trunk. Kadiating lines can be distinguished on the 
end of the log, which represent the organs seen as the smaller scars 
in Figs. 1 and 2. A little to the right of the geometrical center of Fig. 
3 (PI. 31) and a little above it, appears the medullary region of the 
trunk. 
