FAUNAS OF SOUTHEASTERN ALASKA 321 
relative position of the limestone and inferior beds may be the result 
of a fault which has lifted the basal igneous beds considerably higher 
than the limestone at one or more points. On the south shore the 
strike and dip of the limestones and the underlying igneous beds, 
which probably represent submarine volcanic flows, were in harmony 
where observed. In referring to this supposed unconformity the writer 
wishes not to deny its existence, but to point out that further evidence 
is required to demonstrate it. 
The preliminary geological map by Messrs. F. E. and C. W. 
Wright is here reproduced! in order to show the location of the points 
from which the fossils on which this paper is based were obtained. 
The several collecting stations are indicated by numbers, and the 
horizon of each is shown by a geological grouping of the numbers at 
the margin of the map. 
SILURIAN 
The oldest fauna which has been found in the region is of Silurian 
age. A great thickness of rocks, mostly argillites, underlies the 
limestones holding Silurian fossils. These lower beds, in which no 
fossils have been found, have an aggregate thickness of several 
thousand feet, as exposed on the west coast of Kuiu Island. The 
great thickness of these beds and their position below limestones 
known to be of Silurian age strongly suggest their pre-Silurian age, 
although no paleontologic evidence of this has been obtained. 
Two horizons of the Silurian have been recognized. The older 
of these is represented by a small fauna which has been found on the 
northwest coast of Kuiu Island (10).? In the limestones northeast 
of Mead Point the following fauna occurs: 
Diphyphyllum ? sp. Holopea cf. servus Barr. 
Conchidium knighti (Sow.) Murchisonia sp. 
Whitfieldella sp. 
None of the species are abundant, with the exception of C. knighiz, 
which is represented by great numbers of large shells in one thin bed 
of limestone. 
C. knighti is one of the characteristic fossils of the Aymestry 
limestone of the Ludlow group of England. It is known also from 
t Republished from Builletin No. 284, U. S. Geological Survey, 1906. 
2 Locality numbers refer to the map. 
