The devonian goniatites of Devon and Cornwall

Abstract

A description of the devonian goniatites and their localities in Devon and Cornwall is given based upon museum material and new collecting. This enables correlation with the established continental successions and the following German ammonoid faunas have been recognized. The fauna of the Anarcestes Stufe has been recognized in South Devon and probably in Cornwall. Two faunal subdivisions of the Maenioceras Stufe have been recognized, the lowest only at Wolborough, South Devon, the uppermost at Lummaton and Barton, Devon and Trevone and Portquin, North Cornwall (the last two localities have previously been identified with the Cheiloceras Stufe). The three German zones of the Frasnian have been identified in South Devon but only the middle one with certainty in North Cornwall. The Famennian ammonoids have not been exhaustively examined. Only Maenioceras Stufe goniatites occur in the massive lime stones of South Devon which appear to be wholly Givetian in age ; no Frasnian goniatites occur within them but they are found in the thin-bedded or rubbly limestones immediately above. The absence of evidence for the Cheiloceras Stufe emphasises the widespread development of ostracod-slate facies at that time. The recognition of the Gattendorfia and Wocklumeria Stufen (largely the work of others) tells against the large unconformity usually supposed to mark the base of the Carboniferous in South-West England. Ontogenetical details are given for several species: the evidence from Maenioceras shows that it probably evolved direct from Anarcestes or early Wemeroceras. Peculiar internal growths on specimens of Sobolewia shed light on the relation of the soft parts to the shell in goniatites.