XIV.—The Carbonicola Fauna of the Midlothian Fifteen Foot Coal: a Study in Variation

Abstract

The purpose of the following paper is to describe an assemblage of non-marine lamellibranchs found above the Fifteen Foot Coal, one of the lower seams of the Coal Measures in the Edinburgh district. Reference has already been made to this musselband (Weir and Leitch, 1936, pp. 731-732), but, owing to the great diversity of forms present, it was considered advisable to defer the detailed description to a separate paper when adequate illustration could be given. The specimens were collected from several localities in the Midlothian Coalfield, in all cases from above the Fifteen Foot Coal; the majority were collected from Newcraighall Colliery, Niddrie, where they occur in great numbers in blaes with ironstone nodules. Specimens have also been collected by H.M. Geological Survey from the Joppa shore, and from the outlier of Coal Measures at Port Seton Harbour, but these exposures have since been covered up. Most of the fossils are internal moulds, but in many specimens, notably those which resemble C. pseudorobusta Trueman, the shell has been preserved; in these cases the shelly matter is extremely thick, with deep growth furrows. The assemblage shows great variation and, on first examination, might be thought to include several species of Carbonicola and Anthracomya , some of them new, others resembling shells from higher horizons. When viewed as a whole, however, it can be seen that these widely varying forms have a definite relationship to each other, and that all of them can be linked by intergrades to a centre or focus of This 250-word extract was created in the absence of an abstract