THE AGE OF ANTHRACOLITHIC ROCKS F2u 
Pugnax utah is confined to the Schwagerina horizon on the one 
hand and in our rocks is ubiquitous, ranging from the Cherokee 
shales to the Fort Riley limestone. These remarks are also true 
of Ambocoelia planoconvexa which is common to the whole Indian 
Permian. Our ubiquitous Derbya crassa seems to be confined to 
the Omphalotrochus-Cora horizons. Jakowlew has recently shown 
that Meekellia striaticostata is synonymous with M. eximia, which 
makes it ubiquitous in both Russia and America. 
All the pelecypods mentioned below have been found in the Permo- 
Carboniferous of the Donnez, Oka, and Kljasma basins of Russia 
as described by Jakowlew. Only their range in the Kansas deposits 
will be mentioned. 
Pseudomonotis is a group of shells for the most part confined to 
the Permian deposits of the world, though running over into the 
Mesozoic. Nearly all the known species of it found in America are 
found in the Drum limestone, Stage D of the Kansas succession. 
They occur again in the Kickapoo limestone and become especially 
abundant and characteristic in Series IV and above. 
These remarks apply in a general way to Pleurophorus subcostatus, 
the American equivalent of P. costatus. Lima krotowi or its affine 
is confined to StagesI and II. Acanthipecten carboniferus is confined 
to Series I and II and Stages F and G, except a specimen found at 
a much higher horizon in northern Oklahoma last fall. HEntoliwm 
aviculatum has been recorded by Dr. Girty from the Wreford lme- 
stone. Pleurophorus oblongus has only been reported from the Drum 
limestone by Dr. Bennett. Edmondia Nebraskensis ranges from the 
Drum limestone well into the upper part of Series IV.  Schizodus 
wheeleri is found from the Dennis limestone (and perhaps from the 
Fort Scott limestone) into the upper part of Series IV. Streblopteria is 
known from the Drum limestone to the Fort Riley limestone, Dr. 
Girty recording it from the latter horizon. Pleurophorus subcune- 
atus is unknown below Stage J. The Bakewellias and Cyrtodon- 
tarcas have not yet been faunally worked out. A species has been 
recorded from the Willard shales. However, they are very rare until 
much higher strata are reached. 
It will be noted that in the faunal comparisons and discussions, 
the Chase and Marion stages have not been treated quite so fully as 
