MIDDLE LIAS: DORSETSHIRE. 197 
Cretaceous covering that forms the upper part of Golden Cap. 
The higher portions of the Middle Lias can however be studied 
to more advantage in Down Cliffs and Thorncombe Beacon, east 
of Seatown. Here the lower portion of the cliffs consists o blue 
clays yielding Ammonites margaritatus, thus differing from the 
clays at the base of the cliffs under Golden Cap, where A. 
latcBcosta was the characteristic fossil. A fault with a down- 
throw of from 190 to 200 feet accounts for this change, for the 
Three Tiers are depressed beneath the sea-level, and we find 
only the upper portion of the overlying blue clays exposed to 
view. Here, as at Golden Cap, the beds undulate a little, and 
while there they present a gentle synclinal which may have 
helped to preserve the hill, at Down Cliffs and Thorncombe 
Beacon there are two undulations, but the beds on the whole are 
more distinctly inclined towards the east. Thus the thickness of 
the blue clays under the higher portions of these cliffs, varies 
from 50 to 90 feet, decreasing eastwards to about 35 feet at Eype. 
Many small and often fragmentary specimens of A. margaritatus 
may be ootained, sometimes partially embedded in the limestone- 
nodules. Belemnites elongatus, Leda graphica, &c. also occur, 
together with Ammonites Bechei, A. Loscombei, Belemnites 
elongatus, Amber ley a, Trochus, Dentalium etalcnse, Cardium, 
Cypricardia, Pleuromya costata, Plicatula spinosa, Unicardium 
globosum ?, and Rhynchonella serrata ; fossils which I obtained from 
the lower clays exposed between Seatown and Eype, and which 
were identified by Messrs. Sharman and Newton. 
Mr. Day noticed a band of shelly marl beneath the Starfish 
Bed, and obtained from it a number of fossils, including Pleuroto- 
maria anglica and other Gasteropods, Cucull&a, Hippopodium, 
Waldheimia cornuta, Cidaris, Pentacrinus, &c.* 
The Starfish Bed forms a marked layer above these blue clays. 
It is a thick and somewhat nodular or interrupted bed of greenish- 
grey micaceous and calcareous sandstone, stained pink or red in 
places. It attains a thickness of 4 feet 6 inches. The upper 
portion of the masses of rock, is more or less irregular and rounded, 
and sometimes the top layer for 4 or 5 inches splits off. The 
lower surface of the stone is quite smooth and flat, and this splits 
off in thin layers in places. Large blocks of this rock in irregular 
pentagonal and quadrangular masses, sometimes 8 feet across, 
occur on the slopes, or lie strewn on the beach between Seatown 
and Eype ; and where the smooth lower surface of the bed lies 
uppermost and can be examined, it will be seen to be characterized 
by numerous oblong or square holes, extending an inch or more 
into the dense rock. These are spaces whence the Starfishes 
have been chiselled out by fossil-collectors. Hardly a trace of 
these organisms has escaped them even the blocks a short 
distance out at sea have yielded up their fossil treasures. These 
fallen blocks, as well as tumbled material from other beds, form a 
protecting fringe along the coast. Ferruginous springs are thrown 
* Quart. Journ. Geol. Soc., vol. xix. p. 292. 
