Vol. 58. ] SOME GAPS IN THE LIAS. ant 
communis-type do come in at the top of the Ferrocrinoid rock-bed, 
but not lower than a foot below the overlying Transition-Bed. 
’ With the incoming of the Transition-Bed limestones representatives 
of five groups of ammonites appear, not dwarfed but frequently of 
luxuriant growth. They are not represented by a few individuals, 
but by thousands, in which every gradation of growth and ornamen- 
tation seems to find place. Whenever and how they came in we do 
not know. England, France, and Germany fail to supply the 
genetic links of the chain. Perhaps we should look to the Middle 
Lias of Spain and Italy for deposits which may tell us the history 
of this interval of time. The gasteropoda partake much of the type 
of those of the Spiriferina-oxygona Beds, but are mainly of distinct 
specific form—about forty species in all. Polyzoa of like kind occur 
in the Sp.-oxygona Beds at the base of the Ammonites-spinatus zone 
and in the Transition-Bed at the top. 
An interesting part of the record of this time is the alteration in 
the type of the fauna in its spread over the Midiand area.. In the 
outlier of Badby, 14 miles north of Banbury, Mr. Beeby Thompson ' 
found a Transition-fauna, and I have also collected from it. The 
Ferrocrinoidal rock is wasted, and the Transition-fauna occurs in 
holes and pockets in it. A remarkable group of Tellinide replaces 
the ammonites, which are few and dwarfed, and the rock is bored. 
The gasteropoda are dwarfed in size and in ornamentation, though 
very abundant; and the pelecypoda are of small size also. There 
are few corals. At Byfield, 4 miles to the south, the fauna is 
of normal type, as it is also in its easterly spread. At Fern- 
hill, farther south-eastward, the ammonites are of larger growth. 
It may be that this was the coral-fringe of a deeper sea where 
the warmer shallows developed life, as in the inner shoals of the 
Great Barrier-Reef which Prof. Alexander Agassiz has described 
so well. i 
_The Transition-gap, as I have shown, rests for evidence wholly 
upon a sudden appearance of molluscan life of new type. If the 
Ferrocrinoid-bank was reef-like and the development of life went 
on outside it, evidence of the sedimentation in the interval has yet 
to be sought for. The passage of life during the building-up of the 
60 feet of strata of the Ammonites-spinatus zone went on with 
the usual alternating conditions. No one of the ammonites at the 
end of the Middle Liassic day is the same as at its dawn—no one of 
the ammonites of the ‘ spimatus’ beginning lives to the end of that 
time. It is an index of the imperfection of our study of genetic life. 
Turning to the western and south-western side of the Cherwell 
Vale, with the exception of Adderbury which rests on its western 
bank, no remnant of the Transition-period has been found. Farther 
westward, a patch in the Vale of the Stour proves its extension 
there. At Constitution Hill, 1 mile west of Banbury, at Bloxham, 
and Milcombe, 3 or 4 miles farther south-west, the pink and white 
+ «Middle Lias of Northamptonshire’ 1888, p. 43. 
