MIDDLE CHALK IN DIFFERENT AREAS. 
559 
CENTRAL AREA 
(WILTSHIRE.) 
Smooth white chalk 
with two layers of 
flints. 
Soft white chalk in 
thick beds with 
seams of marl, Ter. 
lata and Gal. subro- 
tundus; occasional 
flints. 
Solid white chalk 
without flints, be¬ 
coming nodular and 
passing down into 
hard nodular chalk 
(Melbourn Rock), 
Rhynch. C uvieri and 
Inoc. mytiloides. 
From 80 to 140 feet. 
HERTFORD, BEDFORD, 
CAMBRIDGE & SUFFOLK. 
Massive white chalk 
with flints, Hoi. 
planus. 
Massive white chalk 
with many flints ; 
Ter. lata , Gal. sub- 
rotundus and Inoc. 
Cuvieri. 
Firm chalk with a few 
flints, becoming no¬ 
dular and passing 
down into hard 
nodular chalk (Mel- 
bourn Rock), with 
Rhynch , Cuvieri and 
Inoc. mytiloides. 
About 230 feet. 
NORTHERN AREA 
(LINCOLNSHIRE AND 
YORKSHIRE). 
Top not fixed.. 
Firm white chalk with 
frequent layers of flint 
and seams of dark 
grey clay, Inoc.Cuvieri. 
Hard greyish chalk in 
regular beds full of 
Inoceramus-sheM. Not 
more than 15 feet and 
no harder bed at base. 
Rh. Cuvieri and Inoc. 
mytiloides. 
? 120 to 180 feet. 
Soft grey marl (thin). 
White chalk with 
layers of hard chalk; 
few fossils. 
Greyish white chalk 
with Am. Austeni 
and Hoi. subglo- 
bosus. 
Tough greyish chalk, 
often with siliceous 
concretions and 
layers of harder 
chalk, Am. roto- 
magensis. 
Grey marly chalk with 
Am. varians and 
Inoc. latus. 
Glauconitic chalk with 
iStauronema Carteri. 
Glauconitic sand with 
d m. varians , Am. 
Mantelli and Cato- 
pt/gus columbarius. 
From 230 to 250 feet. 
Soft marl and white 
chalk. 
Whitish chalk with 
few fossils, Hoi. 
trecensis. 
Grey chalk with Hoi. 
subglobosus. 
Totternhoe Stone. 
Tough marly chalk 
passing down into 
soft marl with Am. 
varians , Inoc. latus 
and Rhynch. Alar- 
tini. 
Cambridge nodule bed 
with fossils derived 
from the Gault and 
Aucel. gryphceoides. 
From 180 to 160 feet. 
Soft grey or purple marl. 
Greyish white chalk 
with local bands of 
pink chalk, Offaster 
sphcericus and A m. 
rotomagenis. 
Totternhoe stone. 
Bedded grey chalk with 
Rhynch. mantelliana. 
Rough grey shelly chalk 
with Inoc. latus and 
Am. varians. 
Sponge bed, a pinkish 
limestone with Aucel- 
lina gryphceoides. 
(Absent.) 
Average, 75 to 80 feet. 
(Absent.) 
