Columbia subject headings:
Brachiopoda, Fossil--Wales.
Paleontology--Silurian.
Paleontology--Wales.
Harvard subject headings:
Brachiopoda, Fossil--Wales.
Paleontology--Silurian
Paleontology--Wales.
Princeton subject headings:
Brachiopoda, Fossil.
Paleontology--Silurian.
Paleontology--Wales.
Trilobites.