MIDDLE LIAS : DORSETSHIRE. 
199 
Harbour. They vary from 40 to 55 feet in thickness, and extend 
throughout the Down and Thorncombe Cliffs, obscured here and 
there by a downwash of blue clay from the Upper Lias above. 
Above the sands there is another band of grey marly and sandy 
clay, 10 or 15 feet thick, which is overlaid by the rock-bed that 
forms a junction between the Middle and Upper Lias. 
Mr. Day has recorded from these sandy strata Ammonites 
Bechei, A. spinatus, Nautilus, Belemnites, Avicula, Goniomya, 
Pecten, Pinna, and Plicatula* 
The Junction-bed of the Middle and Upper Lias is made up 
of two layers, the upper of which consists of compact pale pink, 
yellow, or cream-coloured limestone with irregular surface; it 
is much iron-stained in places, and from 1 foot 4 incises to 2 feet 
6 inches in thickness ; from this portion I have obtained Ammonites 
bifrons, A. striatulus, A. serpentinus, and Belemnites. 
The lower layer is a bed of brown, grey and greenish-grey 
iron-shot limestone with nodules, about 8 inches in thickness : it 
contains Rhynchonella acuta, Belemnites compressus, &c. A 
marked ferruginous seam divides these layers, and aids the 
splitting up of the rock. Mr. Etheridge in 1861 detected Upper 
Lias fossils in the upper part of this band of rock, and a short 
time later Mr. Day discovered Middle Lias fossils in the lower 
lower portion of the bed. 
The fossils, perhaps, have not always been collected with a due 
regard to their precise position in this Junction-bed ; and the 
following Ammonites are said to occur throughout it, in both 
Middle and Upper Lias : A. communis, A. serpentinus, A. crassus, 
A. annulatus, and a form recorded as " A. radians " by Mr. Day, 
probably the same as that here noted as A. striatulus.^ 
It is impossible to collect from this bed in situ, owing to its 
inaccessible position, but one can climb up near enough to examine 
its position and general characters : while on the beach after a 
little experience, this and other beds can be readily identified 
among the tumbled blocks. 
The same Junction-bed may however be seen in a brickyard 
and in the road-cutting north of Allington, where the section is 
as follows : 
Upper Lias. 
Middle 
Lias. 
r Brown and blue micaceous and 
I sandy marls - 
Pale compact and pink-stained 
limestone ... 
Brown and blue ironshot lime- 
stone with veins of calc-spar - 
Brown sandy micaceous marls 
with Belemnites 
Brown and blue ironshot lime- 
stone with Belemnites, Rhyn- 
chonella ... 
Yellow sandy micaceous marls 
! Yellow micaceous sands. 
6 feet shown. 
9 in. to 1 ft. 6 in. 
8 in. to 11 in. 
3 ft. 6 in. to 4 ft. 
10 in. 
4 ft. shown. 
Quart. Journ. Geol. Soc., vol. xix. p. 293. 
Day, Quart. Journ. Geol. Soc., vol. xix. p. 284. 
