14 ALASKA GEOLOGY 



remains of marine algae it is fair to assume that this also is of that 

 nature. There may be recent algae with which it might be compared, 

 but we know of none reticulated like this one among the fossil forms. 



Locality. Pogibshi Island opposite the village of Kadiak, Alaska. 



Collectors. G. K. Gilbert, B. K. Emerson, Charles Palache. 



Genus Gyrodendron gen. nov. 



Plant consisting of apparently solid cylindrical stems, bifurcating 

 one or more times, and enrolled in one plane so as to form one or 

 perhaps two volutions ; inner extremity somewhat acuminate, outer 

 ends obtuse. 



In the absence of any characters beyond the mere form we must 

 place this peculiar type with such other supposed remains of algae as 

 Cylindrites, Helminthoida and Helminthopsis, from all of which it 

 is at once distinguished by its spiral habit of growth. Whether the 

 stems were originally solid or hollow can not be decided now. As 

 preserved, their composition is generally quite different from that of 

 the matrix in which they are embedded. 



Gyrodendron emersoni sp. nov. 



Pl. XVIII, fig. 3; Pl. XIX, figS. I, 2. 



Stems varying in thickness from 2.5 mm. to 6.0 mm., bifurcating 

 once, twice or three times, all apparently becoming more robust with 

 age and forming from one to one and two-thirds volutions about the 

 acuminate inner extremity. In the larger examples the concentric 

 curve of the outer ends of the branches is gradually lessened until 

 they become approximately straight and appear to run off at a tangent. 



This striking and easily recognized fossil is named in honor of 

 the eminent geologist, Prof. B. K. Emerson. 



Locality. Pogibshi Island, opposite the village of Kadiak, Alaska. 



Collectors. G. K. Gilbert, B. K. Emerson, Charles Palache. 



Genus Gilbertina gen. nov. 



Plants ? consisting of a double cord wound in a close spiral like 

 the spring of a watch. As preserved, the fossils present the appear- 

 ance of a slender coiled tube cut in half horizontally. 



This remarkable fossil can at present be compared only with Hel- 

 minthoida Schafhautl, though we are not by any means satisfied that 

 there is any true relationship between them. Much might be said 

 upon the possible relations of Gilbertina, and also concerning other 

 interpretations of its fossil remains, but it may all very well be post- 



