63 
but that future investigations made, lead to very unexpected 
and unlooked for results. Hasty generalizations in Science 
are always to be deprecated and avoided. 
The Rheetic ‘bone bed,’ as before stated, is present at the 
base of the Lias, and reposes immediately on the Red Marl, 
the top of the Trias or new red sandstone. Generally it 
forms one thin stratum, of a dark colour, almost black, 
charged more or less with pyrites, and is entirely composed 
of the rolled and comminuted fragments of fish and Saurians. 
In some places there are two or three distinct ‘bone beds,’ * 
divided by shale, limestone, or coarse sandstone, and some- 
times there is a band of limestone, often arenaceous full of 
bones, coprolites, and teeth. Whatever the matrix may be 
in different localites, and however variable in thickness, it is 
always characterized by the same organic remains. It 
probably attains its greatest thickness at Aust Cliff, on the 
banks of the Severn, in Somersetshire, where it contains 
some large palatal teeth of the remarkable fish Ceratodus. 
From Westbury Cliff I obtained a very large vertebra of an 
Icthyosaurus, indicating a Saurian of great size. Long be- 
fore the strata at the base of the Lias were assigned to the 
Rheetic; holding an intermediate position between that 
formation and the Trias, my friend Sir Philip Egerton our 
great authority on fossil fish, from the peculiar character 
of those in this bone bed, referred it to the upper New red 
sandstone. Some are peculiar to it, and others belong to 
species which prevail in the Muschelkalk, a calcareous, and 
* At Watchet there are three separate ‘bone beds,’ the first is a thin conglomerate 
of bones and teeth, a little more than two inches thick, underlaid by a sandy marl* 
with similar fossils, two feet thick. Still lower is a sandy stratum, bone bed, 
with quartz pebbles and limestone nodules, with same fish remains as in bone beds 
above, somewhat more than two inches thick. Black shale, and then another bone 
bed, with same and additional fossils, two to three inches. Shells peculiar to the 
Rheetics occur more or less in all these bone beds, but belong to different genera, 
some being common to each. Rolled fragments of large reptilian bones are also 
noticed here by Mr, Dawkins, and one hollow bone supposed by him to belong to 
a Pterodactyle, 
