— 469 — 
distinctly rectangular with slightly rounded angles, while the others 
are frequently polygonal; medullary rays very large ond profuse, 
varying from 1 to 35 cells in height and from 1 to 4 cells in 
width, generally fusiform, sometimes attenuate and sinuate, rarely 
more than two tracheides distant from one another, ray cells 
varying, much in size in transverse section, sometimes reaching 
a height of 120 microns and averaging 80 microns or more, 
usually narrwer than high, relatively oblong and narrow trans- 
versely in the narrow rays ant polyyonal in the broader rays, 
distinctly rectangular and muriform in radial section, the radial 
diameter considerably exceeding the tangential, frequently by over 
one and one-half times the latter. 
The species described above is represented in the collection bya 
single fragment 7.5cm in longitudinal diamster, 6 cm in radial and 
7,5cm in tangential diameter. The specimen is weathered a little and 
has b2en slightly rounded onone side, probably prior to deposition. 
The fragmentisevidently from an arborescent type of large proportions, 
since the convergence of therays on the opposite sides of the block is 
hardly perceptible. Nothing is known as to primary wood or cortex. 
The soft texture of the xylem has resulted in several zones of defor- 
mation, which appear, however, to be totally independent of any diffe- 
rence in structure. 
The tentative reference of this wood to Scgillaria is based merely 
on the evidently great development of the secondary xylem in the 
type. It may represent the xylem of one of the species described on 
the preceding pages. We must remember, however, that the genera 
Sigillaria and Lepidodendron cannot always be distinguished by the 
characters of their internal organization even when the primary wood 
is well preserved, the only decisive criteria being those offered by 
the surface of the stems. The features of the body of the exogenous 
wood offer no means for a generic separation. 
Sigilaria ? muralis is specially characterized by the profusion of 
the muriform rays, the great sizeof the medullary cells, the regularity 
of the xylem wedges, and the occasionally very large size of the 
tracheides which are distinctly reticulate in contact with the ray 
cells. 
In the specimen described aboveI have not observed any bundles 
that seem to traverse the medullary rays in route to the leaves, and, 
