224 
THE EHAETIC BONE BEDS 
It is evident that the late Edward Wilson had this tlieory 
in his mind when he wrote in his paper on the “ Rhsetics 
at Stanton, Notts,” ^ these significant words : “ Since these 
beds were, in all probability, the resulting deposits of 
migratory shoals, and not of a universal swarm of fishes, 
a certain amount of time must be allowed for their transit 
from one place to another.” 
In effect, these deposits may be termed “ Submarine 
Guano Beds,” though as regards their bulk they are but 
trifling when compared with modern instances of a like 
character ; for instance, the guano beds of the Chincha 
Islands and other places in South America have shown 
thicknesses of 50, 60 and even 100 feet. This is more 
striking when we remember that these enormous masses 
were deposited by birds within a period geologically 
recent. 
Summary. 
These are the plain facts as observed in the Bone Beds, 
and the conclusions which they indicate. In order to 
make the principal points clearer, the following abstract 
or summary may be useful : — 
1. The “ Bone Bed ” is not a regular or persistent bed, 
but a series of thin sheets (or lenticules) of varying extent, 
coming in at various horizons and deposited at various 
times. 
2. These sheets are separate and have no connexion 
with each other, except that they are of common origin, 
the general structure and fossils being identical. 
3. They are chiefly caused by the Saurians and car- 
nivorous fishes, being the remains of their victims, with the 
addition of coprolites, etc. 
4. The extent of each sheet was determined by the size 
1 Quart. Journ. Geol. Soc., xxxviii. p. 455. 
