THE AGE OF ANTHRACOLITHIC ROCKS pat) 
In strong contrast with the brachiopods and bryozoans stand 
some of the pelecypods. They are not paracmic and do differentiate 
with changing conditions, and constitute the main characteristics 
of the upper part of the Kansas section. This differentiation seems 
to have been in the main closely parallel in direction with the devel- 
opment of the Permian pelecypods of Europe. 
It is to be regretted that the ammonoid cephalopods were nearly 
wanting in the Kansas basin throughout its faunal history. The 
trilobites are represented in the upper rocks by a single species of 
Griffithides, the last (so far as the Kansas rocks are concerned) of 
the Proetidae. Many of the ostracods are to be looked upon as degen- 
erate or atavistic, and probably are not found above the rocks of the 
Chase stage. 
The study of the stratigraphy of the Kansas basin and its surround- 
ing deposits and its fauna, has convinced me that the foregoing general 
considerations must be taken into account in order to reach a rational 
understanding and interpretation of its faunal history. It should 
also be held in mind that the evolution of a fauna, in so far as it is 
capable of evolution, in this great epicontinental sea is of as great 
significance, as the evolution of a fauna along similar lines about the 
islands and in the continental seas of Europe. On account of its 
limitations and relative paracmic condition the latest fauna of the 
Kansas basin, without free contributions from other regions which 
physical conditions seemed to prohibit, cannot be expected to con- 
tain the wealth of species characterizing cosmopolitan faunas. 
In the study of the Anthracolithic section of Kansas the following 
stages and larger divisions here designated “series” have been made 
out. These divisions with their characteristic faunas are described 
in Vol. IX of the Kansas survey, in press at this writing. 
The basal formation of the Kansas Pennsylvanian system is the 
Cherokee shales or Stage A. This stage is characterized by a pre- 
ponderance of specimens of Marginijera muricata with an abundance 
of Chonetes mesolobus, etc. It might with propriety be called the 
Marginijera muricata Zone, as in no other horizon is this species 
the predominating one. Stage B is characterized by the introduction 
of a very large number of the most characteristic Coal Measures 
~ fossils, sixty species being added in its basal member, the Fort Scott 
