126 ANIMALS OF THE PAST 



more difficult problem, since the pieces are not 

 like so many checkers — all made after one pat- 

 tern — but each has an individuality of its own. 

 The total number of vertebree must be guessed 

 at (perhaps it would sound better to say esti- 

 mated, but it really means the same), and 

 knowing that some sections are from the front 

 part of the vertebral column and some from 

 the back, we must fill in the gaps as best we 

 may. The ribs offer a little aid in this task, 

 giving certain details of the vertebrae, while 

 those in turn tell something about the adjoin- 

 ing parts of the ribs. We finish our Tricera- 

 tops with a tail of moderate length, as indica- 

 ted by the rapid taper of the few vertebras 

 available, and from these we gather, too, that 

 in life the tail was round, and not flattened, 

 and that it neither served for swimming nor 

 for a balancing pole. And so, little by little, 

 have been pieced together the fragments from 

 which we have derived our knowledge of the 

 past, and thus has the palaeontologist read the 

 riddles of the rocks. 



To make these dry bones live again, to 

 clothe them with flesh and reconstruct the 



