MIDDLE LIAS : DORSETSHIRE. 201 
tatvs and A. spinatus. The Ufargaritatus-stone, together with 
the highest beds, present characters resembling the Marlstone of 
other places, and the fossils also lead me to include this portion 
of the series in the zone of Ammonites spinatus ; leaving the 
underlying beds down to the Three Tiers in the zone of A. 
margaritatus. The range of A. Loscombei and A. Bechei into 
these lower beds of the Middle Lias is noteworthy, but I am 
unable personally to confirm it. (See p. 203.) 
The Three Tiers form locally a good division between Lower 
and Middle Lias, but these bands have nowhere been identified 
inland, and, as before noted, the rock might easily be confused 
with the Starfish Bed. Near Banbury there are some hard bands 
in the lower beds of the Middle Lias that recall the Starfish Bed 
of the Dorsetshire coast. 
In tracing the Middle Lias inland in Dorsetshire we have, as 
before mentioned, few sections to guide us in fixing the boundary 
with the Lower Lias, while the Upper Lias clay is not sufficiently 
well-marked to have been distinguished on the Geological Survey 
Map. Moreover the area between Beaminster and Bridport is 
much faulted, so that when isolated exposures of micaceous sands 
are to be seen it is difficult at unce to determine whether they belong 
to the Middle Lias or to the Midford Sands. Thus north of 
Watton Hill, Bridport, a lane-cutting showed micaceous yellow 
sand and rock-sand, overlaid by hard beds of micaceous and 
calcareous sandstone these beds pass under the Upper Lias beds 
exposed in the brickyard north of Ailington, and are thus of 
Middle Lias age, although represented on the Survey Map as 
Midford Sands. 
The Marlstone Junction-bed was observed by Mr. Bristow on 
the road leading from Bothenhampton to Shipton Gorge, and 
about half-way between the two churches: but it is so thin that 
it is rarely seen until we reach the district near Ilminster and 
Yeovil. In 1887 the same bed was found by Mr. J. F. Walker 
in Shipton Long Lane. The Marlstone (1 ft.) contained Ammo- 
nites spinatu?, and was overlaid by a conglomeratic bed, containing 
A. bifrons, A. communis, and worn specimens of A. falcifer. 
Similar beds were noted by Mr. Walker in a deep cutting in 
Shute's Lane, Symondsbury.* 
The micaceous sands are well shown in some of the deep lane- 
cuttings in Dorsetshire, one of the most remarkable of which is 
between Colmers Hill and Leazacre, at Symondsbury near 
Bridport. The cutting shows micaceous yellow sand with hard 
bluish calcareous sandstone in places. 
Through Dorsetshire and Somersetshire the boundary of Lower 
and Middle Lias, as represented on the Geological Survey Map, 
has been taken approximately where the more marked feature occurs 
at the base of the comparatively porous sandy shales of the 
Middle Lias, and about the horizon of the Starfish Bed of the 
coast section, as the underlying bine clays throw out strong 
* Geol. Mag., 1892, p. 440. 
