[PENHALLOW] NORTH AMERICAN SPECIES OF DADOXYLON 65 
only four. The slit-like orifice is diagonal and nearly the full diameter 
of the pit. The most characteristic feature is to be found in the 
peculiar distribution of the bordered pits, which occur in well defined 
groups of about 6-13, while the groups themselves fall into radial series. 
These facts were correctly noted by Dudley, but they have been entirely 
unnoticed by Dawson? and also of Knowlton,* whose diagnosis of this 
species is simply compiled from that of Dawson. The character is 
nevertheless an important one (fig. 12), since it is the one feature which 
alone, will differentiate this species from all others. In a tangential 
section, the rays are seen to be numerous, 1-2, more rarely 2-seriate, 
and varying from 24-55 mic. in width. The oval or round cells are all 
thin walled. From these facts the following diagnosis may be derived : 
Transverse.—Tracheids about 44 x 55 mic., the walls about 12.5 mic. thick. 
Radial.—Ray cells resinous and starch bearing, long and narrow, about equal 
to 3-7 tracheids, the ends conspicuously narrower; the pits on the 
lateral walls 3-6, chiefly 4 per tracheid, the slit-like orifice nearly the 
full diameter of the pit. 
Bordered pits numerous, round, about 9.3 mic. broad, distributed 
in radially disposed groups of about 6-13; the orifice diagonal, nearly 
the diameter of the pit. 
Tangential.—Rays of medium height, 1-2, rarely 5-seriate in part; from 24-55 
mic. broad, the oval or round ceils all thin walled. 
CORDAITES CLARKII, Dn. 
Figs. 8, 16. 
Bib. :—Dawson, Foss. Pl. of the Dev. & U. Sil. Form. of Canada, 1882, 125; 
Knowlton, Proc. U. S. Nat. Mus., XII., 607. 
Dist.—Hamilton Group, Ithaca, New York. 
This species was founded upon material obtained from the Genesee 
shales at Lake Canandaigua, New York, by Prof. H. M. Clarke, and was 
first recorded by Sir William Dawson in 1882.* 
The material in my hands shows a well developed pith composed 
of large, thin-walled cells, many of which contain starch. There is 
also evidence of an abundance of resin which is apparently contained 
in specialised cells, but this fact could not be ascertained satisfactorily. 
In a transverse section the elements of the protoxylem are not specially 
differentiated from those of the surrounding tracheids which show the 
4+ Jn’1 Cincin. Soc. Nat. Hist., 1889, 54-55. 
? Geol. Surv. Can., 1871, 14. 
8 Proc. U. S. Nat. Mus., XII., 606. 
* Foss. Pl. of the Dev. & U. Sil. of Can., 1882, 125. 
R Sec. IV., 1900. 5. 

