BEVAX MARINE SHELLS OF THE SOUTH WALES BASIN. 507 



the colliers, when they have struck this rock, consider that they lose 

 all further traces of coal. This is, however, a misnomer, for there are 

 in it two or more seams of coal, generally thin, but often good and 

 workable, and a good deal of ironstone. These seams are termed 

 Eosser veins," and I think it advisable that the term Pare- 

 well Eock " be discarded, and the name " Eosser Eock " substituted. 

 It is in these seams that a bed of marine shells occurs, which I have 

 traced for more than fifty miles along the greater portion of the north 

 crop — in some places occurring in coal-shale, in others in ferruginous 

 clay and ironstone. It is probable that the early condition of these 

 beds was that of a huge delta or estuary, and that the mollusca sought 

 the shelter of the bays, that they might enjoy comparatively still water. 

 They are all of the mountain-limestone series, as the following list 

 will show, and it is interesting to notice that the carboniferous lime- 

 stone shells were not cut off entirely at a certain period or line, but 

 that some species found their way very high up into the true coal- 

 measures. I have obtained from these beds — 



Actinocrinus 



Modiola 



Cythere (species) 



Mytilus 



Athyris planosulcata 



Myacites angulata 



Chonetes Hordrensis 



Sanguinolites 



C. variolata 



Unio 



Discina nitida 



Venus elliptica 



Lingula mytiloides 



Conularia quadrisulcata 



L. elliptica 



Holopella 



Orthis filiana 



Macrocheilus 



0. Michelini 



Murchisonia 



0. resupinata 



Natica vetusta 



Productus Flemingii 



Turritella 



P. concinnus 



Goniatites falcatus 



P. semireticulatus 



G. Listeri 



P. spinulosus 



(j. reticulatus 



Spirifer pinguis 



Bellerophon hiulcus 



Aviculopecten 



B. Urii 



Axinus carbonarius 



Nautilus 



A. sulcatus 



Orthoceras cinctum 



Edmondia 



0. scalpratum 



Nucula tumida 



0. (n.s) 



N. laevirostrum 



The next zone of life that we find is in the shale of the bottom vein, 

 which is a seam of coal from 1 ft. 6 in. to 2 ft. in thickness, lying on 

 the Eosser Eock. In these shales are scattered fish-remains, jaws, 

 teeth, palates, bones, rays, and scales, belonging to Amhii/pierus, Cten- 

 acanthus, Helodusy Ctenoptychius, Palceoniscus, SoloptycMus, Codacantlius, 

 andPsammodus, while one shell only has been found atEbbw Yale, Spirifer 



2 o 2 



