Columbia subject headings:
Harvard subject headings:
Geology, Stratigraphic--Permian
Geology--Texas
Invertebrates, Fossil--Texas.
Paleontology--Permian
Paleontology--Texas
Princeton subject headings:
Geology, Stratigraphic--Permian.
Geology--Texas.
Invertebrates, Fossil--Texas.
Paleontology--Permian.