THE CARBONIFEROUS LAMELLIBRANCHIATA OF 

 THE CLYDE DRAINAGE AREA. 



BY JAMES NEILSON. 



THIS class of the mollusca ranges throughout the several divisions of the 

 Carboniferous rocks, the marine species being met with in the greatest 

 numbers in the shales and clay-ironstones alternating with the limestones, in 

 which latter, however, comparatively few specimens are found. 



The freshwater, or brackish-water group, represented by the Carbonicola, 

 Anthracomya, and Naiadites, are confined chiefly to the musselband iron- 

 stones and shales of the Upper Carboniferous series, a few species being got 

 in similar strata in the Middle Coal and Ironstone series, while one 

 Naiadites crassa is found in shale under the lowest limestone in the Beith 

 district, associated with marine fossils. None of this group are to be met 

 with in any of the beds yielding the characteristic marine organisms of the 

 system, while, on the other hand, none of the latter are found in the Middle 

 Coals and Ironstones. In several instances where Carbonicola is said to 

 have been got along with marine organisms it may probably have been 

 derived from some earlier deposit, or drifted seawards from its own proper 

 habitat, or even more probably, it may have been picked up on a shale-heap 

 amongst marine fossils, having really been derived from quite a different 

 stratum, as recently happened in the case of other fossils at Alexandra Parade,. 

 Glasgow. It is evident that these freshwater or brackish- water forms 

 have lived in the Scottish coal-field under quite different conditions from 

 the marine ones found in the Limestone series. 



In the following list the names of the freshwater group are those given 

 in Dr. Wheelton Hind's Monograph on Carbonicola, Antkracomya, and 

 Naiadites, and those of the marine Dimyaria in his Monograph on the 

 Carboniferous Lamellibranchiata, both issued by the Palaeontographical 

 Society, 1894 to 1900. Unfortunately Dr. Hind has not yet worked out 

 the Monomyaria, though it is to be hoped he will soon do so, as at present 

 the group is in a most unsatisfactory condition. When this is done we are 

 under the impression that the number of species will be very much reduced. 



Many of the generic and specific names in this list will be found to differ 

 from those in the 1876 Catalogue 1 owing to various causes, such as the 

 sub-division of genera, the former names being synonyms of previously- 

 existing species, or former faulty identification of the species. For facility 

 of reference to the existing literature on the subject the old names have been 

 given in italics, and within brackets ( ). 



MONOMYARIA. 



Leiopteria lunulata, Phill. (rare). U. L. S. Gare : Thornliebank. L. L. S. 



Howrat, Dairy. 

 L. squamosa. TJ. L. S. Thornliebank : Garpel Water, Muirkirk. 



1 Catalogue, of the Western Scottish Fossils, Glasgow, 1876. 



