THE CARBONIFEROUS GONIATITE GENERA GIRTYOCERAS AND EUMORPHOCERAS

Abstract

I. Introduction Northwest European Upper Visean and Lower Namurian strata contain certain small and medium sized goniatites that resemble one another closely by virtue of their similarly lenticular or discoidal shape, often acute-edged, and by the occurrence of a ventral sinus and a pair of ventro-lateral salients (linguae); in some forms such salients are marked by a transcrescent groove; in late forms, short ribs occur on the sides of the shell between the umbilicus and the ventro-lateral grooves. These shells, in recent years, have usually been referred to the genera Sagittoceras Hind, Eumorphoceras Girty, or Homoceras Hyatt. In this paper the validity of these and other genera is discussed and new species of the genera Girtyoceras and Eumorphoceras are founded, mainly on specimens collected from the Bowland Shales of the Pendle and Skipton areas in the north of England. In the course of this work and in its presentation the author has received much help from many friends: to them and in particular to W. S. Bisat, G. Cotton, R. G. S. Hudson, C. J. Stubblefield, and R. Webber he is sincerely grateful. Part of the expenses of the work were paid for by money allocated to the author from the Government grant in aid of scientific investigations which is administered by the Royal Society. The Director of the Geological Survey of the United States kindly provided the photographs of the holotype of Eumorphoceras bisulcatum Girty. Finally the author records his thanks to the Yorkshire Geological Society for the generous ...