=I 
bo 
UPPER CAMBRIAN. 
Upper BALA Group, Sedgw. (restricted in 1866. The Upper Bala of the Synopsis includes the 
Bala limestone, now Middle Cambrian). 
1. Hirnant Limestone and Llanfyllin beds—viz., pale coloured slates above the Bala limestone. Ash Gill 
slates, &c., above the Coniston Limestone. 
2. Llandovery Rocks (Phillips, Salter, Lyell—Lower Llandovery of the Survey). 
The fossils of these two divisions are arranged together in the cases and drawers, as it is clearly impossible 
always to draw a line between them; and they form indeed one series. But the list is kept in two separate 
columns here, as each group contains a few peculiar species. And it may eventually be proved that No. 2 is 
unconformable on No. 1. The conglomerates and grits of the Llandovery rock do not appear everywhere under 
the covering of the Silurian rocks, because these are unconformable on them. But wherever we rise to beds far 
above the level of the Bala limestone, a profusion of corals, Bryozoa and Brachiopoda of the smaller kinds, take 
the places of the characteristic Bala limestone shells. I arrange Ash Gill beds (above the Coniston limestone) 
with this division; but not that upper portion of the Coniston flags known as the Brathay flagstone, for that 
is the base (or nearly) of the Silurian series. 





Case and , 
Column of IEE porence ee Oy S Names and References: Observations, &c. Numbers and Localities. 
Drawers. |SYBopsis: and Figures of Genera. 
Upper Bala proper. Llandovery Group. 
Nidulites, Salter. So called from a.185,Mullock quarry, 
its resemblance to the egg cap- Dalquorhan, Girvan. 
sules of marine Gasteropods espe- 
cially of Natica. The differences 
are obvious. 
Gu Sponges ? Nidulites favus, Salter (Quart. Jour. | [This is one of the 
Paleopora favosa. Geol. Soc. Vol. vi. p. 174; Siluria, | commonest of fossils 
Veil, iL Gh, iver, Bh jo, 1s}, 
in part only. 

ty 


3rd ed. Foss. 30, fig. 3). A curious 
fossil, having exactly the aspect 
of miniature honey-comb. The 
structure is as follows: a thin 
undulated plate, to which are 
attached on each side minute 
hexagonal cups (a pit at the base 
of each shews the point of attach- 
ment), alternating in either face, 
just like the comb cells, but with 
a length and breadth of only a 
line. 

in the same forma- 
tion at Haverford- 
west. Kindred forms 
are probably to be 
sought in Sphero- 
spongia, a middle 
Bala fossil. ] 

