READING THE RIDDLES OF THE ROCKS 103 



reptiles known as Triceratops whose remains are among 

 the treasures of the National Museum at Washington, 

 for the reconstruction of the big beast well illustrates the 

 methods of the palaeontologist and also the troubles by 

 which he is beset. Moreover, this is not a purely 

 imaginary case, but one that is very real, for the skeleton 

 of this animal which was shown at Buffalo was restored 

 in papier-mache in exactly the manner indicated. We 

 have a goodly number of bones, but by no means an 

 entire skeleton, and yet we wish to complete the 

 skeleton and incidentally to form some idea of the 

 creature's habits. Now we can interpret the past only 

 by a knowledge of the present, and it is by carefully 

 studying the skeletons of the animals of to-day that we 

 can learn to read the meaning of the symbols of bones 

 left by the animals of a million yesterdays. Thus we 

 find that certain characters distinguish the bone of a 

 mammal from that of a bird, a reptile, or a fish, and 

 these in turn from one another, and this constitutes the 

 A B C of comparative anatomy. And, in a like manner, 

 the bones of the various divisions of these main groups 

 have to a greater or less extent their own distinguish- 

 ing characteristics, so that by first comparing the bones 

 of extinct animals with those of creatures that are 

 now living we are enabled to recognize their nearest 

 existing relative, and then by comparing them with one 

 another we learn the relations they bore in the ancient 

 world. But it must be borne in mind that some of the 

 early beasts were so very different from those of to-day 

 that until pretty much their entire structure was known 

 there was nothing with which to compare odd bones. 

 Had but a single incomplete specimen of Triceratops 

 come to light we should be very much in the dark con- 

 cerning him; and although remains of some thirty 

 individuals have been discovered, these have been so 



