THE GONIATITES OF THE BEYRICHOCERAS ZONE IN THE NORTH OF ENGLAND

Abstract

I. Introduction. This zone, approximately of Middle Visean age, was, together with the succeeding P zone, the period of greatest evolutionary activity in the goniatite fauna of the Carboniferous era. For the first time we meet with practically the whole of those stocks, which either unchanged or in their derivative genera, were to play such an important and at times dominant part in the fauna of the Middle and Upper Carboniferous. Indeed the fresh evolutionary outburst in the Permian period of other areas concerned just those stocks which we see first in zone B. For the first time we make the acquaintance of the genus Goniatites, s.s. The genus Dimorphoceras appears and introduces secondary saddles in the main lobes. The newly arrived genus Beyrichoceras and the allied genera Beyrichoceratoides and Sagittoceras appear to be the ancestral genera of all our dominant Middle and Upper Carboniferous goniatites. The Prolecanitids shew a sudden burst of evolutionary activity, and new genera such as Pronorites and Daraelites 4 are seen for the first time, curiously enough to disappear again, except in Minorca7, until the close of the Carboniferous period. Zone B marks also the last appearance of the Devonian genus Aganides 2. The material on which this paper has been based, in addition to specimens in my own collection, has been loaned by various collectors and officials of museums. I am especially indebted to Dr. R. G. S. Hudson, Mr. F. W. Anderson, Dr. D. Parkinson, Dr. J. W. Jackson, Mr. E. W. J. Moore, Mr.