80 LIVERPOOL BIOLOGICAL SOCIETY. 
TAIMEBUODE. Fs... desde ccassccees Tears ee eee ee 
Gl aVil, Sir sape ssc Ble eueeu ca teks 0 tet sonia enn iene mene 2 ge: 
Nodular limestone i:25.2-.2 set oem ears ere Siar 
Mottled pyritous shalest.(22.7..tectove, oe ren ere en een 
Lamestone: 2000s. ea Se ee ee ee ee 
Pyritous clay with lenticular patches stained 
“purple; yellow and blue anv0t)., <a vet eae lO aes 
Impure hematite or reddle .............0.ceseeeeee lou 
Nodular limestone, embedded in sandy matrix, 
stained and cemented by red hematite, 
the nodules increasing in size and number 
LOWards therpase cece eas erecta eer 16 feet. 
Thick massive hmestone to base of cliff. 
The nodule bed is the best fossil collecting ground on 
the island, as the fossils have weathered well out in relief 
and are more easily extracted from these nodules than 
from the solid limestone. The hematite band, of which 
one specimen yielded 9°2 per cent of iron, can be followed 
along the cliff till it dips level with the church, below the 
sea. The limestone itself calls for no special comment 
as it is of the normal type, but the shale bands demand 
more attention. Their origin can be regarded either as 
due to the occasional deposition of layer of shale by the 
irruption of floods of muddy water into the carboniferous 
limestone sea, or as due to the accumulation of the in- 
soluble residue of the limestone along the lines of drainage 
of the water, that percolating through the rock removes 
some of it in solution as bicarbonate of ime. .In many 
cases, especially in the North, these shale bands are 
unquestionably due to the former cause, but those on 
Puffin Island may be regarded with greater probability as 
analogous to the marl bands of the Chalk, many of which 
are certainly due to causes operating long subsequently to 
