XIV INTRODUCTION'. 



Geology deals with the Earth, the composition of the various 

 strata, or layers, of which it consists, their pi-esent and former 

 extent, and the physical conditions under which they were 

 deposited, and the changes they have since undergone. 



Palseontology deals with the remains of ancient life found 

 in the various layers, and strives, by comparison with living 

 forms, to restore the successive faunas and floras which have 

 passed away, and to trace by those relics their past dis- 

 tribution, and thus to show the evolution of life on the earth 

 from the earliest times to our own. 



So many good books on Geology and Palteontology have 

 been published * that it is not necessary to give in such a guide- 

 book as the present a treatise on the science, but merely to 

 explain that the Vertebrata in the Galleries are arranged 

 according to their zoological classes, orders, and families (so far 

 as these can be ascertained) ; and upon the label to each is 

 placed its name, its geological position, and the locality whence 

 it was derived. In the Invertebrata and Plants each class is 

 also grouped chronologically in order, from the latest deposits 

 to tlie earliest in which it occurs. 



Whenever a specimen has been figured and described in a 

 scientific work, a green disk is affixed to it, and a reference is 

 given to the author, and to the name and date of the work 

 where it was published. 



Explanatory labels and illustrations have been introduced in 

 many instances, to afford fuller information to visitors respecting- 

 the objects exhibited. 



A plan of the Gallery will be found affixed to the wall in 

 each room, which will serve to show the general arrange- 

 ment of the cases and their contents. The small Table of 

 Strata, on p. xii, is given to indicate the i-ange in time of the 

 great groiips of Mammals, Birds, Reptiles, Pishes, Invertebrates, 



and Plants. 



H. W. 



* See sijecially " Manual of Pala?ontolog_T," by Prof. H. Alleyue 

 Nicholson and R. Lydekker, in 2 vols. (3rd Edition). Wm. Blackwood and 

 Sons, Edinburgh and London. 1889. 



