Re vie w of Recen t Geological Liter a ture." 2 49 
basins. Their drift deposits, largely till, attain maximum thick- 
nesses of 100 to 150 feet. 
Ground ice, forming low sea cliffs, sometimes 30 feet high, 
overlain by a foot or two of muck, which is carpeted with moss 
and grass, occurs along distances of several miles at Halkett and 
Simpson capes, midway between the mouth of Colville river and 
Point Barrow. 
Placer gold mining on the head streams of the Koyukuk river 
has yielded somewhat more than $700,000 during the years 1899 to 
1903, this being the only mineral resource utilized in the vast re- 
gion thus traversed between the Yukon and the Arctic sea. 
Bituminous coal and lignite of fair quality have considerable 
development on the Anaktuvuk and Colville rivers, and also at sev- 
eral localities on the Arctic coast, where coal in beds from 1 to 16 
feet thick has been occasionally mined during the past twenty-five 
years by the crews of whaling and revenue vessels. The coal-bear- 
ing formations probably range in age from the Jura-Cretaceous to 
the Oligocene Tertiary. South of tfie mountains, the same forma- 
tions, with veins of coal and lignite, occur on John and Koyukuk 
rivers, and one coal vein seen on the latter stream has a thick- 
ness of 9 or 10 feet. 
Snow was found to average about six feet deep in the Koyukuk 
valley in April, 1901, but two months later it had melted away 
from the lowlands of that district. w. u. 
On the Origin of the Marine {Halolimnic) Fauna of Lake Tangan- 
yika. By W. H. HuDLESTON, F. R. S. Journal of Transactions 
of the Victoria Institute, London, vol. xxxvi, 1904, pp. 300-3.51, 
with two plate maps and four figures in the text. 
Lake Tanganyika, about 400 miles long, 2,700 feet above the 
sea and having a great depth, lying in a very remarkable north 
to south rift valley or graben, has numerous distinctly marine types 
of moUusks, crabs and prawns, jelly-fishes, sponges, etc., associated 
with its ordinary fresh-water fauna. The lake qutflows, in its flood 
stages, by the Lukuga river to the Congo. None of the many other 
lakes of the same large group, in east central Africa, has such a 
mingling of species nearly related to marine forms with the fresh- 
water species. 
Mr. J. E. S. Moore, who visited lake Tanganyika in 1S96 and 
again in 1899 for thorough studies and collecting of its fauna, has 
pointed out resemblances of its halolimnic gasteropods to fossil 
species of the Inferior Oolite in the Jurassic series of England and 
France. The author of this paper, however, deems these resem- 
blances inconclusive for derivation of the Tanganyika gasteropods 
from the Jurassic. More probably the connection of this lake with 
the sea, and its separation and uplifting of the valley, belonged to 
a much later geologic period: for the prolonged graben system, 
in which this valley is a part, appears to date its origin from Middl',- 
Tertiary time. w u 
