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. Dall. 



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 Cymopolia 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 puncta3. 



1 Both P. singulare and P. textum were identified by Heer in rocks, formerly 

 at least, referred to the Lias. In the Flora Fossilis Helvetiae, 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. 



