166 W. D. Carr—On the Lincoln Lias. 
Owing to surface metamorphism the upper 3 or 4 ft. of shale is. 
altered to a tenacious yellow clay, which contains in its lower part 
fossils changed to a bright yellow; crystals of selenite are found 
where the yellow clay merges into the blue, and the clay there has 
a rotten appearance. Included also in the yellow bed are septarian 
nodules presenting a very curious wrinkled appearance, being exactly 
like gigantic kidneys; these when traced into the blue beds quite 
lose this character and appear as depressed spherical masses having 
a hard polished surface often covered with small shells. 
This kidney-like appearance is due to the partial and unequal de- 
composition of the mass. The veins of calcite which traverse the 
septarium in all directions are harder than the indurated clay that 
goes to form the bulk of the nodule, and stand out in relief. When 
decomposition is more pronounced, the veins of calcite stand well 
out from the nodule, and present much the appearance, only on a 
larger scale, of one of the Paleeozoic chain corals. 
Crossing the valley that the river Witham has cut through the 
Oolitic escarpment, we find on the south cliff a series of three sec- 
tions in different brick-pits which expose nearly the whole of the 
‘Lias down to the top of the Capricornus zone. The upper pit, be- 
longing to Mr. Best, is in Upper Lias, and the same beds containing 
the same fossils are traceable in the upper part as in the pit belong- 
ing to Messrs. Swan. Continuing the section here about the same 
horizon at which we left off on the north cliff, we find about 20 
feet of blue clay, containing occasional Belemnites and crushed 
shells, and below it a calcareous gritty band of shale, containing 
many Belemnites and a few other fossils. Leaving this pit, and 
entering the second, we again take up the section, and find one 
foot below this last gritty band two thick beds of argillaceous 
limestone separated by five feet of clay. The upper limestone is 
less sandy than the lower, and rather ferruginous, and the lower 
shows occasional traces of concretionary action. On weathering 
they readily split up into very thin laminz, and pieces are readily 
detached a couple of feet across having an uniform thickness of not 
more than one-sixth of an inch. These limestones form the base of 
the Upper Lias, which is here about 90 feet thick, and no doubt — 
represent the first and insect limestones of other districts, though the 
only fossils found in them are Inoceramus dubius and Ammonites ; 
small fragments of the shells of Inocerami are found scattered 
between the lamine, and might occasionally be mistaken for fish 
scales or fragments of the elytra of beetles. The fossils of the 
Upper Lias are tolerably numerous and well preserved (with the 
exception of the Ammonites, which are seldom perfect), and are 
interesting as including several new forms; there is also a remark- 
able absence of common Upper Lias species, Nucula Hammeri, for 
instance, taking the place of Zeda ovum, the latter common shell 
being absent. Below is a full list of fossils :— 
SAURIA— PiscEs— 
Ichthyosaurus sp. Hybodus sp. 
Plesiosaurus sp. 
