WME SOAONG GIHAN GES TN PAUINAID, GEO GIA PINE) 343 
boniferous region. Again here we see the intermediate charac- 
teristic between the eastern American and Eurasian faunas, but 
the affinities are closer with the latter. 
The McCloud limestone corresponds to the upper part of 
C,, and the lower part of C, of the Russian section. The upper 
part of the McCloud limestone is, therefore, homotaxial with the 
zone of Omphalotrochus whitneyi, Meek. This species was first 
described from the McCloud limestone, but has been found in 
eastern Russia near the top of C, in such large numbers as to 
give name to the zone. 
Artinsk beds.—The argillites above the McCloud limestone 
are the equivalents of the Robinson beds of the Taylorsville 
region and of the Little Grizzly creek beds of Plumas county. 
These are probably homotaxial with the top of C,, and the lower 
part of the Artinsk stage of Russia. They contain the following 
species closely related to forms of the Russian Artinsk stage, 
and the Productus limestone of the Salt Range in India: 
Margintfera conf. splendens, Norwood and Pratten. 
Productus conf. cora, d’ Orbigny. 
6 conf. scabriculus, Martin. 
“ conf. spzralis, Waagen. 
ff group of P., abichi, Waagen. 
Streptorhynchus conf. pelargonatus, Schlotheim. 
Camarophoria conf. furdonz, Davidson. 
Dielasma elongata, Schlotheim. 
Spirifer interplicatus, Rothpletz. 
S. (Reticularia) lineatus, Martin. 
S. wynnet, Waagen. 
In addition to some of these, the Robinson horizon of Plumas 
county contains a very long slender /usulna that agrees closely 
with #. Jongissima, Moller from the Salt Range. 
Of the above mentioned species Marginifera cont. splendens is 
the form usually identified with Productus longispinus, Sowerby in 
the Western Upper Carboniferous. Productus conf. spirals is 
only a mutation of P. semireticulatis, Martin; Spirifer wynnei is a 
modification of S. striatus. Thus this fauna stands to the Carbon- 
iferous forms as mutations, showing only a slight difference in 
