138 
ALASKA GEOLOGY 
num and P. textum , in the shales of the Flysch formation, generally 
regarded as of Eocene age, and possibly also in the Liassic. 1 
Locality .— Woody Island, Kadiak. 
Collector .— W. H. Dali. 
Genus Arthrodendron gen. nov. 
Plant ramose, bushy, the branches constricted at regular intervals 
and probably consisting each of a series of rounded or ovate, flattened 
(originally inflated) joints; surface of joints minutely granopunctate. 
This marine plant may have some relation to Cymofolia Lamouroux 
and Corallina Linn., but instead of a thick calcareous incrustation the 
joints appear to have had a leathery carbonaceous cover that, in con¬ 
sequence of the compression the plants have suffered in common with 
the mud in which they were entombed, is now thickened around the 
edge of each joint and more or less wrinkled in the flattened space in¬ 
closed by the marginal rim. The substance of the plant, which is be¬ 
lieved to have been carbonaceous, because of its dull polish and dark 
color, is readily distinguished from the grayish-black shale in which 
the specimens are embedded. 
The jointed or beaded character of the branches, coupled with their 
carbonaceous composition, recalls an Eocene (Flysch) species from 
Switzerland that Heer refers to the recent genus Hormosira Harvey. 
In the fossils before us, however, the joints appear to be of one kind 
only, whereas in Hormosira two sets — one narrow and sterile, the 
other wider, subglobular, and fertile — are distinguishable. 
Arthrodendron diffusum sp. nov. 
pi. XIV, figs. 1-3. 
Branches moniliform, springing from a central point and spreading 
outwardly and upwardly so as to form a loose bush-like mass as much 
as 15 cm. in diameter; divisions dichotomous, at intervals varying 
from 6 mm. to over 20 mm. Joints subelliptical, the lower half 
usually a little narrower than the upper half, 4 mm. to 6 mm. in 
length and from 2.2 mm. to 2.8 mm. in width; surface usually glossy 
and smooth, but where the preservation is more favorable is covered 
by minute granules and punctae. 
1 Both P. singulare and P. textum were identified by Heer in rocks, formerly 
at least, referred to the Lias. In the Flora Fossilis Helvetia, however, he 
doubts the Liassic age of the beds, and seems to favor the view of Escher, who 
had previously suggested that they belong to the Eocene. Whether this later 
view has been substantiated by more recent investigations we can not say. 
