Growth and variation in the non-marine lamellibranch fauna above the Sand Rock Mine of the Lancashire Millstone Grit

Abstract

Shells from a recently discovered band of non-marine lamellibranchs above the Sand Rock Mine (near the top of the Millstone Grit Series) west of Wigan have been statistically investigated at four localities. The dominant fauna, Carbonicola exporre ta gar and variants, is systematically described and the variation analysed. The affinity of this fauna appear to lie with Carbonicolidae characterizing lower horizons in the Namurian, whereas a second group of shells, much less commonly represented in the band, shows similarity with the succeeding faunas of Anthraconaia bellula (Bolton) and Carbonicola fallax Wright.