4 GUIDE TO THE FOSSIL INVEETEBEATE ANIMALS. 



STEATIGEAPHICAL SEEIES AND HISTOEICAL 

 COLLECTIONS. 



Gallery XI. Hanging on the wall of Gallery XI, immediately to the 

 left of the entrance is a diagram showing very broadly the 

 Geological Epochs during which the rocks found in Great 

 Britain were formed, the newest being at the top and the 

 oldest at the bottom of the column. A more elaborate list, 

 with the Epochs divided into Ages, is given as a table 

 (facing p. 1) in the present Guide. 



Wall-cases Adjoining the diagram, in the wall-cases on the west side 

 of the gallery, is the Stratigraphical Series, which is a 

 collection of the various kinds of rock found in Britain, 

 arranged in order of age. Along the top of the Cases is a 

 diagram showing the succession of these rocks from the 

 newest to the oldest, as they might be seen in a continuous 

 section across the country from east to west. Examples of 

 the rocks themselves occur on the shelves below, where will 

 also be found numerous small sections of the strata, as 

 observed in various parts of England. Affixed to the Cases 

 is a series of small maps, each coloured to show the tract of 

 country occupied by the one or two rock -groups of which 

 specimens are exhibited in the adjoining Case. In the long 

 section, the numbers placed beneath the beds give their 

 approximate thicknesses in feet. It must not, however, be 

 supposed that all these beds occur in such regular succession 

 right through the country, the fact rather being that one is 

 found in one district, while another is better developed 

 elsewhere, as indeed may often be gathered from the names 

 applied to the beds. Certain gaps in the section, as between 

 Pliocene and Eocene, and again between Permian and the 

 Coal Measures, represent intervals of time, during which 

 there were being deposited rocks, which are found in other 

 parts of the world, but for one reason or another do not occur 

 in the British area. 



It is plain that when rocks have been deposited, as we 

 know that they now are being deposited at the bottom of 

 the sea, then the underlying rocks are older than those above 

 them. As concrete examples of the way in which one layer 

 of rock is found lying on another, there are placed on the 

 floor between the Wall-cases in various parts of the Gallery 

 several examples of the cores of rock brought up from below 

 Between by deep borings. Thus at Dover the boring for coal went 

 down through the Chalk at the surface, through several rocks 



