A statistical investigation of the Anthracomyas of the basal Similis-Pulchra Zone in Scotland

Abstract

In a recent paper on “the Zonal Distribution of the Non-marine Lamellibranchs in the Coal Measures of Scotland” (Weir and Leitch 1936) the lower boundary of the Similis-Pulchra Zone was defined by a fauna that occurs above the Musselband Coal of the Central Coalfield, above the Three-Foot Coal of Douglas and below the Wee (Hurlford Main) Coal of North Ayrshire. The fauna contains a rich and varied assemblage of Anthracomyas which were determined as A. adamsi Salter sensu lato. In defining the fauna as that of the base of the Similis-Pulchra Zone, reference was made to the fact that in England and Wales the normal A. adamsi is typical of a much higher horizon in the zone (above the Mansfield Marine Band and its equivalents); on the other hand, certain of the associated Carbonicolas (C. affinis and C. turgida) are typical of horizons that have been interpreted as high in the Modiolaris Zone (Wright's Affinis Subzone).