64 LIAS OF ENGLAND AND WALES; 
Extracrinus briareus, mostly coated or replaced by iron- 
pyrites. (See p. 70.) 
The Coin Stone Bed is the name applied to the upper portion 
of a band of large cement-stones, that forms two and sometimes 
three layers. They occur in the top of the middle clay-terrace 
of Black Ven, and form a noticeable band, about 40 feet beneath 
the pale-grey Beleumite Beds, in the cliffs of Stonebarrow to the 
east of Cnarmouth. A large cut and polished Septarian-limestone 
with Ammonites stellaris (now in the Museum at Jermyn Street), 
was obtained by Robert Hunter from one of these huge cement- 
stones. Dr. Wright observes that the nodules often contain very 
large specimens of A. obtusus and A. Brookei, the veins of spar 
in the rock intersecting and distorting the fossils.* 
Immediately above these beds we enter the zone of Ammonites 
oxynotus, specimens of which are prevalent in the dark pyritic 
shales and clays about 10 feet above the Coin Stone Bed. The 
variety of this species known as A. lymensis, and A. densinodus 
likewise occur. 
Still higher in the same set of shales, A. armatus and A. 
raricostatus occur, but there is nothing to indicate any plane of 
demarcation between the zones. I obtained one specimen of A. 
raricostatus from the beds on this horizon east of Charmouth, but 
it extends upwards into the Belemnite Beds above. 
These higher beds of shale are however more impregnated 
with iron-pyrites than is the case lower down, although this 
mineral is more or less abundant throughout the Black Marl 
Series. It was however from this upper portion that much 
pyrites was at one time obtained, during the winter months, for 
the manufacture of sulphuric acid ; and there is a band in the 
shales known as the " Metal Bed." 
The series now under notice extends to the base of the upper 
terrace under Black Ven, where two or three bands of limestone 
occur at the junction with the Belemnite Beds. These bands 
were mostly obscured in Black Ven by talus (in 1884), but were 
shown in the cliffs of Stonebarrow on the east. 
The Black Marl thus includes the zones of Ammonites obtusus, 
A. oxynotus, and A. raricostatus, which here and elsewhere may 
be conveniently linked together. Here the beds yielding A. 
obtusus form by far the greater portion of the series, the zonal 
Ammonite (according to Dr. Wright) being found at various 
horizons between the Hard Marl and the Coin Stone Bed : but 
the associated species are not many. Dr. Wright records Am. 
Bi?-chii, A. Brookei, A. stellaris, A. planicosta, A. sauzeanus, and 
A. xcmicostatus.^ 
Some of the cement-stones near Charmouth have been em- 
ployed for making cement, and remains of a disused cement-mill 
still stand near the sea-shore. 
* Lias Ammonites ( Palaeoutograph. Soc.), p. 50. 
f Lias Ammonites, Pal. Sue., pp. .">(), 51. 
