DESCRIPTION OF ADDITIONAL SPECIMENS. 333 
4. Here we see again a form of foreshortened, truncated bolster, com- 
parable in form to that of Lepidodendron clypeatum Lx. Within the bol- 
sters we have a very obtuse-angled prominence occupying a position at 
the base of the large boss. This transverse or flatly deltoid scar may be 
regarded as representing the horizontal side of the oval-triangular cen- 
tral area in the specimens previously noted. Within this angle, the 
thickened walls of which are suggestive of the leaf scar, we see the horse- 
shoe-shaped loop including one or two small cicatrices. Indications of 
the more orbicular or prominent development of the large boss are seen 
at “a” on the cortex on the left, or in the partially decorticated area on 
the lower right. 
A better understanding of this fragment, which has been removed from 
the left branch of the trunk illustrated in plate 22, figure 1, may, how- 
ever, be reached by an inspection of the opposite side of the same speci- 
men which is shown, enlarged to twice the natural proportions, in plate 
23. The conditions seen on the surface of the cortex of this specimen 
are as follows: Within a broad, diagonally truncated bolster, suggestive 
of those of certain Lepidodendra, we have, as before, near the middle, a 
prominence in the form of a very obtuse angle, opening upward.* The 
protruding walls of this angle rise slightly and increase in thickness in 
approaching the center, where they in some instances form a very low 
deltoid area. The periphery of this transverse area exhibits for a dis- 
tance of from 1.75 millimeters to 2.1 millimeters on either side of the 
center a rugose surface of carbonaceous matter, surrounded apparently 
by a line of separation. ‘The area inclosed by this fractured carbonaceous 
rim can hardly be anything else than the leaf cicatrix; and I may add 
in this connection that none of the other specimens on which the outer 
tissues are preserved seems to show any other definite evidence of frac- 
ture or separation on the surface of the bolsters. From the lateral an- 
gles of these leaf scars, which are often slightly crescentic, pass narrow 
vanishing ridges which may lie in the same direction as the correspond- 
ing side of the cicatrix-‘‘angle,” or they may curve somewhat upward 
before vanishing in the, border of the large boss which they help to de- 
fine. The vanishing ridges and crescentic prolongations probably play 
an important part in preserving the roundish, distinct outline of the 
boss seen in the impressions earlier described. It must be remembered 
that on the cortex of the stems the interior surface of the large bosses is 
slightly concave. A resemblance to the impressions is seen in several _ 
of the bolsters in the abraded and partly decorticated portion on the 
* The orientation of the figure is based on the plan of the fragment in the dichotomized trunk, 
pl. 22, fig. 1. The interpretation of this prominence as leaf sear, though somewhat tentative, pre- 
serves the Lepidodendroid analogy in the bolsters. 
