140 ROMER’S DESCRIPTION OF THE CHALK 
The formations which we have in the preceding pages referred 
to the lower greensand, are true sandstones; in which, exclu- 
sively, the following fossils appear to occur :— 
Exogyra columba. Inoceramus concentricus. 
Pecten zequicostatus (var. major). Cardium Hillanum. 
Pinna quadrangularis. vee > ING piame 
..- decussata. Nerinea Borsoni. 
depressa. 
If we compare this list with the large number of fossils which 
have been described in England from the lower greensand, the 
latter will appear to be remarkably poor with us; but we shall 
find that the two following formations completely counterbalance 
this disproportion. 
2. Hils-conglomerate. [Hils-conglomerate. | 
This formation generally presents itself as a mass of granules 
of quartz and silicate of iron, which are cemented by a yellowish 
or gray, ferriferous calcareous marl. 
The most westerly occurrence is in the district of the Ruhr, 
at Essen. Here the old coal formation predominates; but this 
in most places supports a horizontal layer, about 10 feet in thick- 
ness, of the conglomerate, which at the Hagenbecker Zeche ap- 
pears as a greenish, small-grained, tolerably compact sandstone ; 
but at other points as a yellowish-gray, highly ferruginous loose 
sand, with numerous grains of silicate of iron. On the western 
side of the town this formation,—which hitherto has been re- 
ferred to the upper greensand, to which indeed it is very similar 
in mineralogical respect,—is covered by the gray chalk (plener). 
The Hils-conglomerate is found to contain still more iron at 
Steinlahte, close to Salzgitter in the valley of the Innerste; in 
the lower part are here yellow and blue slaty loams,—followed, in 
ascending order, by a yellow tolerably compact sandstone 25 feet - 
thick,—which is succeeded by pure oolitic ironstone 7 feet in 
thickness,—separated by a thin stratum of a compact ironstone, 
from a sandy oolitic ironstone 5 feet in thickness ; this last sup- 
ports a very considerable mass of red, yellow and gray slaty loams, 
and these are succeeded by the streaked marl and gray chalk © 
(flammen-mergel and plener). The thickness of the deposit — 
increases, in other points of the same range of hills, to 160 feet. 
A third occurrence of the conglomerate is at Vahlberg on the © 
