272 MR. E. A. WALFORD ON [May 1902, 
limestones of the Upper Lias (Ammonites-communis zone) are welded 
with the Middle Liassic Ferrocrinoid-Beds ; the whole of the inter- 
vening Transition-Bed, fish-bearing limestones, and paper-shales of 
the Amm.-serpentinus zone have been wasted. As far as the north- 
western escarpment near Shennington there is the same hiatus, and 
Ammonites bifrons is in the same rock-course as the spinatus-fossils. 
The interval must be looked upon as a belt of waste, such as the 
Inferior Oolite limestone shows at the base of the argillaceous beds 
of the Bathonian. Inter-waste seems to me a convenient 
term to define the removal of strata long subsequent 
to their deposition. 
A succeeding gap, though in point of waste of strata repReaennedl 
best by the absence of 3 feet 2 inches of clays and limestones, yet 
corresponds with the 193 feet of the same series at Alderton’ in 
Gloucestershire, and with the 50 or 60 feet of the zone of Ammo- 
nites serpentinus in Yorkshire. In point of paleontological time it 
includes :— 
The genesis and expiry of groups of minute brachiopoda (Lep- 
tena, Thecidea, etc.) and of many of the gasteropoda and 
pelecypoda. Charles Moore, in 1867,’ made out 70 species 
from his Leptena-beds. 
. The genesis of many large falciform ammonites and of the 
Belemnitidee of the fish- and insect-beds (zone of Posidonomya 
Bronnt of French authors); also its numerous gasteropoda, 
noticeably Huomphalus ninutus. The first appearance of 
6 species of saurians, 8 species of fishes, 6 forms of crustacea, 
and of many of the insecta and microzoa. 
In all, adding the Somerset lists to those of the Midlands, quite 
400 distinet species, fully one-half of which have not been collected 
or recorded from strata above or below the gap. Yet it is excep- 
tional in the Midlands to meet with the fragmentary remains even 
of the beds which hold so important a record of life. Middle 
Liassic rock merges into high Upper Liassic rock without a line of 
interval or separation. Before the many processes of interstratal 
waste were understood, the gaps were put down to cessation of 
deposit, contemporaneous erosion, and like causes. 
A curved band drawn through Central England from Yorkshire 
to Somerset, widening at the two ends, puts before us the waste of 
this gap in the Midlands, where yet the Middle Liassic rock rests at 
an altitude of 720 feet. The broadening of the band to the north- 
east and to the south-west indicates the remaining greater thickness 
of strata there. 
A third gap of minor importance, both in its waste of strata 
and in its change of life-forms, can be measured in Oxfordshire and 
Northamptonshire by the occurrence of a thin bed of Pentacrinite- 
limestone. The layer is recognizable, owing to its being made up 
wholly of crinoid-segments. It is found to the north at Byfield in 
Northamptonshire, and southward as far as Souldern in Oxford- 
. Quart. Journ. Geol. Soe. vol. xxiii (1867) p. 449. 
