SEVAN — 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 "Fare- 
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 moUusca 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 oif 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 
Chonetcs Hordrensis 
Sanguinolites 
C. variolata 
Unio 
Discina nitida 
Venus elliptica 
Lingula mytiloides 
Conularia quadrisulcata 
L. elliptica 
Holopella 
Orthis filiana 
Macroclieilus 
0. Michelini 
Murchisonia 
0. resupinata 
Natica vetusta 
Product us Flemingii 
Turritella 
P. concinnus 
Goniatites falcatus 
P. semireticulatus 
G. Listeri 
P. spinulosus 
G. retlculatus 
Spirifer pinguis 
Bellerophon hiulcus 
Aviculopecten 
B. Urii 
Axinus carbonarius 
Nautilus 
A. sulcatus 
Orthoceras cinctum 
Edmondia 
O. scalpratum 
Nucula tumida 
0. (n.s) 
N. Icevirostrum 
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 AmUypterus, Cten- 
acanthus, Selodus, Ctcnoptychius, Falmoniscus, HoloptycMus, CmlacantJms, 
and Psanimodus, while one shell only has been found atEbbwVale, Spirifer 
2 o 2 
