Columbia subject headings:
Graptolites.
Paleontology--England.
Paleontology--Ordovician.
Paleontology--Wales.
Harvard subject headings:
Graptolites--Great Britain.
Graptolites--Wales.
Paleontology--Great Britain
Paleontology--Ordovician
Paleontology--Wales.
Princeton subject headings:
Graptolites.
Paleontology--England.
Paleontology--Ordovician.
Paleontology--Wales.