XXXI. Notes on some Carboniferous Lamellibranchs, their mode of Occurrence and observed Shell Structure

J. Young
1882 Transactions of the Geological Society of Glasgow  
IN the strata of our upper coal measures, as well as in the coal measures that form the middle division of the Scottish Carboniferous limestone series, we find a small group of mytiliform shells, which were formerly referred to the marine genus Myalina; but as they were found not to possess the thick hingeplate of this genus, and to differ in some other particulars, they were erected into a new genus in 1863 by the late J. W. Salter, under the name of Anthracoptera-literally coal-wing-from
more » ... found in strata alternating with our coal-seams, and this name has since been retained. The genus is represented in our beds by at least three species, Anthracoptera carinata, A. modiolaris, and A. quadrata. These are often found to be associated in the same beds with the group of shells formerly termed Coal Unios, but which have now received the generic names of Anthracosia and Anthracomya. These three genera seem to have been gregarious in their habits, their shells being seen to enter largely into the composition of our mussel-band ironstones, and mussel-band oil shales. Formerly this group, from being found associated in some localities with strata containing marine shells, was also believed to be of marine origin. But this has always been a point of doubt in the minds of many palaeontologists, especially as this group of mollusca has never yet been met with in the same stratum along with the typical marine organisms of the period. The belief is now largely entertained that the Anthracosia group of shells lived in fresh-water lakes and estuaries, at times brackish, and which, from oscillations of the land, may have been covered by the sea over certain tracts for a period, marine conditions in the strata that lie over, and sometimes alternate with, the fresh water shell beds, being thus brought about. As far as Scotland is concerned, I have never observed any commingling of true marine fossils in any of our mussel-band beds. The reptiles, fishes, molluscs, annelids, ostracods, and other organisms belong to 16, 2015 at Rice University on July Downloaded from
doi:10.1144/transglas.6.2.223 fatcat:qvtmjr3gq5fwvies6q3ubrzjyi