218 
THE KHAETIC BONE BEDS 
be noticed erect, or even reversed. Now, the great 
majority of the fossils in these Bone Beds conform to the 
first rule of tranquil deposition, and not to the second or 
“ drift ” rule. A very small proportion are in any way 
heaped up, and these few instances can be easily accounted 
for by local disturbances or irregularities in the underlying 
beds. 
A further interesting feature is the comparative absence 
of molluscan remains in the Bone Beds, so few being found 
that they might almost be said to be non-existent. This 
is a curious fact, and indicates that we have to deal with 
deposits different from the stratified beds in which they 
occur, as in many instances the latter are crowded with 
shelly remains. Another point is, that while the adjacent 
beds usually show well marked lines of stratification, in 
the Bone Beds they are frequently obscure or altogether 
absent. (This statement does not apply to the thin 
sandy beds, which generally have the lines.) 
“ False ” or Atypical Bone Beds. 
It will be noticed that the term “ True Bone Bed ” is 
used, suggestive of other or “ False ” Beds. It may be 
as well to briefly indicate what these are, and in what 
points they differ. 
(1) Drift Beds. The first is a “ Drift Bed,” which 
is sometimes erroneously classed as a “ Bone Bed.” 
It is a soft bed, usually black claj^ or marl, and is 
the result of current or wave action cutting into the 
Bone Bed before consolidation, and drifting off a 
portion of its contents for deposition elsewhere. It 
may be known by its soft nature, by having but 
few fossils, and those of the lighter and smaller sorts 
