MM. Chapman and Sherborn—Ostracoda of the Gault. 345 
that I possess are pale grey in colour, and occurred in a loose block 
of grit low down in the wood near Gell Fachreth. The faulting 
here, which brings down the Arenig ashes, may also have lowered 
the grit of Moel Cors-y-garnedd. 
A series of sections from typical pisolitic and oolitic ironstones of 
N. Wales has facilitated this comparison; but the bodies in the grits 
of Rhobell evidently consist largely of ferrous carbonate, and have 
not undergone the reduction to magnetite from which most of the 
oolitic ironstone beds have suffered. This is the only evidence I 
possess of the occurrence of a ferrous carbonate stage in these deposits, 
though it has previously been hinted at’ during a discussion of their 
mode of origin. 
After assigning these concentric bodies to the layers of Arenig 
ironstone, it is strong support to find that Messrs. Jennings and 
Williams” have observed pebbles derived from the oolitic ironstone 
‘in a grit of the Arenig series in the Moelwyn area. 
II. —On Tor OsrrRAcoDA OF THE GAULT AT FOLKESTONE. 
By Freperick Cuapman, F.R.M.S., 
and C. Davies SHERBORN, F.G.S. 
(PLATE XIV.) 
INCH the year 1885 the various zones of the Gault at Folkestone 
have been systematically examined by one of us for the purpose 
of recording the Foraminiferal fauna of that deposit; the report 
upon which is now being published in the Journal of the Royal 
Microscopical Society. 
At the same time the Ostracodal valves were isolated from the 
washings with the view of a similar report being made upon them ; 
and it is thought that the publication of the results will be of some 
interest, in showing the distribution and relative abundance of these 
minute animals through the various deposits laid down in the Gault 
sea of that locality. 
The extreme profusion of certain forms in particular beds is 
remarkable, and this segregation of species is often referable to the 
lithological differences met with in the various strata. (The nature 
of the deposits in the various zones and horizons is described in 
detail in the publication before mentioned.)* The slight connecting 
links of the Gault with the Jurassic Ostracoda on the one hand, 
and with those of Tertiary age on the other, have an additional 
-paleeontological interest. 
But few new forms were met with, and this is strong testimony 
to the lifelong care bestowed upon the Cretaceous Ostracoda as a 
whole by Professor T. Rupert Jones. The results of his labours are 
-embodied in a supplementary monograph of the Cretaceous Hntom- 
ostraca of England and Ireland (Pal. Soc. 1890), of which we have 
' Cole and Jennings, ‘‘ Northern Slopes of Cader Idris,’ Quart. Journ. Geol. Soc. 
vol. xlv. p. 427. 2 Loc. cit. p. 374. 
3 F. Chapman, The Foraminifera of the Gault of Folkestone, parti., Journ. Roy. 
Micro. Soc. 1891, pp. 566-572. 
