140 
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 algaa 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. 
pi. xvm, fig. 3; pi. xix, figs. 1, 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- 
