THE RHAETIC BONE BEDS 
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(scales and teeth), such as would drift easily, and the 
comparative absence of the larger and heavier fossils ; 
also, it has well marked lines of stratification. 
(2) Beach Beds. The second is a “ Beach Bed.” 
The Rh^tic sea, like other seas, had beach deposits, 
of which we find examples, notably at Redland. This 
bed comes pretty close to the “ Bone Bed ” in 
character, being frequently hard and crystalline, but 
it agrees with the “ Drift Bed ” in the poverty of its 
fossils, both in number and size, and also in the 
well marked stratification, but the principal difference 
is that it is largely composed of broken shells, which are 
wanting in the “ True Bone Bed.” 
As these two beds are often mistaken for the Bone Bed, 
it is advisable to point out in what respects they differ, 
and then proceed with our subject. 
Contents of the Bone Bed. 
A “ True Bone Bed ” will be found to contain five princi- 
pal constituents : ( 1 ) Bones ; (2) Teeth ; (3) Scales ; (4) 
Coprolites ; (5) Quartz pebbles. Any bed containing less 
than four of these, or only a small amount of them, should 
be carefully examined, as it may be only a “ Beach ” or 
Drift Bed.” 
It may seem odd to say that a Bone Bed should contain 
bones, but it has more than once happened that a bed 
with only a few teeth and scales, and no bones, has been 
termed the Bone Bed. This is incorrect, as otherwise the 
whole range of Upper and Lower Rh^tics would have to 
be -classed as “ Bone Beds,” not a single bed being quite 
