THE AGE OF ANTHRACOLITHIC ROCKS 721 
role in the later faunas. They are: Pleurophorus whitei, Aviculo- 
picten nebraskensis, and Myalina permiana and a species usually 
referred to M. aviculoides. A species of Schwagerina associated 
rather closely with a Permo-Carboniferous micro-foraminiferal 
fauna also occurs in this stage. During this stage, too, some of the 
most characteristic and cosmopolitan species of the Kansas Pennsyl- 
vanian are found for the last time. Four of these are: Spirijer came- 
ratus, Hustedia mormoni, Spiriferina kentuckiensis, and Chonetes 
geinitzt (not C. laevis of Keyes). 
Stage J is important in that it records the final reduction of the 
Fusulinas to the ranks of a rare species, in possessing a very abundant 
ostracod fauna of a late type, and the final occurrence of ten or fifteen 
species. 
The Chase stage, the upper part of Series IV, is characterized by 
the development of the pelecypods and the lessening of the réle 
played by the Molluscoidea. The abundant forms are: a retro- 
gressive form of Seminula argentia, a species of Fenestella, Pro- 
ductus nebraskensis, Bairdia beedet or an allied form, with other 
ostracods, Septopora sp., Derbya multistriata, Mylina permiana, 
Aviculopecten nebraskensis and a form of A. occidentalis, Myalina 
aviculoides ?, several species referred to Bakewellia, Pleurophorus 
whitet, with two other species, Pseudomonotis hawni, Edmondia 
nebraskensis, Aviculopinna knighti, A. nebraskensis, Producti of the 
semireticulatus type, and a Derbya like D. crassus and a species of 
Rhombopora. 
Above Series IV, the brachiopods and bryozoans and ostracods 
and other lower groups nearly disappear, leaving an impoverished 
pelecypod fauna. ‘The fauna of the Red Beds of Oklahoma and the 
Panhandle of Texas, lying one or two thousand feet above the Marion 
stage, has already been described." 
The following table is expressive of the numerical relationship 
of Series IV to Series I-III: 
Species 
No. of Species No. o Species in Common 
Derlesp lege eho aide .o exe Legh ON anos Aas SenesmiViee ice PAT i veiots ete ie 51 
Serleswlil sys ta ijccecsicce reyes DG geen eRe Series WVicese aaensat TAM card testorcocie ene 73 
Seniespllltlive eran ciin. =: BOAlga es tere: SOLTCS MV ies seach TAD ie yee olexete 85 
« “Invertebrate Pal. Upper Permian Red Beds of Oklahoma and Panhandle of 
Texas,” Kansas University Sci. Bull., 1V, pp. 115-71, 1907. 
