Columbia subject headings:
Cephalopoda, Fossil--England.
Cephalopoda, Fossil--Wales.
Paleontology--England.
Paleontology--Ordovician.
Paleontology--Wales.
Harvard subject headings:
Cephalopoda, Fossil.
Paleontology--England.
Paleontology--Ordovician
Paleontology--Wales.
Princeton subject headings:
Cephalopoda, Fossil--England.
Cephalopoda, Fossil--Wales.
Paleontology--England.
Paleontology--Ordovician.
Paleontology--Wales.