— 593 — 
organism. Accordingly the specimens illustrating the differente forms 
and varying details will be describad somewhat fully. 
The specimen photographically shown in natural size in Pl. x, 
Fig. 3, suggests by its form, and thick midrib a foliar organ. It is the 
only specimen eshibiting either bilateral symmetry, or the presence 
of what may possibly be interpreted as a median nerve. The coun- 
terpart or impression of this specimen is shown in Fig. 4. The 
tubercles on the intermediate zones of the lamina in this example are 
rather distant and of medium size. They, like the midrib, are slightly 
darker on account of the denser brown iron stain on the surface, 
which, on the tubercle, is generally a liltle smoother than on the inter- 
vening lamina. 
There is practically no carbonaceous residue adhering to this or 
the other specimens of theorganism, except a slight granular residue 
in some of the tuborcular impressions shown in Tig. %, and a few other 
fragments. The rounded proximal end of the tubercle is very little 
prominent and often indistinct, but the distal end rises somewhat and 
is sharply defined, as illustrated, enlarged from another example, in 
Pl. xi, Fig. 3. 
The minate, punctiform, umbilicoid scar, rig. 5, Pl. xi, is placed 
at the distal apex of the tubercle in this specimen and it often is 
scarcely depressed, being rather in slight relief (1). 
The margim is distantly cut in nearly vertical short narrow teeth 
the apices of which turn backward as minute concave points. 
The midrib is broad, at the base, persistent to the extreme apex, 
and flattened, the border being indistinct in portions. It is evidently 
thick and immersed in the thick substance of thelaminaasis shown 
hy the flattened cast in lenticular cross section, and especially where 
the cast is broken away, as illustrated in portions of the counterpart, 
Pl. x, Fig. 4 (2). 
The lamina, bearing normal tubercles, is seen to extend con- 
tinuously beneath it. The surface of the midrib is densely crowded 
with minute and somewhat irregular low seales or scaly tubercles, 
wl more prominent distally, and possibly a very little imbricated. 
(iI Tr egret to have to explain that the light is, ly error, from the right in some 
cf the pho!ozraphs. Reference to the text will show whether the specimen is in relief or 
depressed; ani inversion of the plate will then correct the photographical error. 
(2) The t:ue aspect of the impre:sion will be presented if the figure is inverted. 
5560 64 
