84 THE THEORY OF EVOLUTION 



less different in the successive chapters, may repre- 

 sent the forms of life which are entombed in our 

 successive formations and which falsely appear to us 

 to have been abruptly introduced." l 



An excellent example of the imperfectly recorded 

 facts is afforded by the long and narrow, but very 

 thick belt of rocks, which forms the surface of the 

 Connecticut Valley and runs unbrokenly from the 

 Hudson River across New Jersey, Pennsylvania and 

 Maryland into Virginia; the whole formation is 

 referred to what geologists call the Triassic period. 

 These rocks, which were not laid down in the sea, 

 but on land and in various bodies of fresh water, 

 are remarkably barren of fossils and one may search 

 through great thicknesses and over weary miles with- 

 out finding a trace of ancient life. In several local- 

 ities, notably in western Massachusetts, were exten- 

 sive mud-flats, which have preserved countless 

 foot-prints of the great variety of reptiles then 

 inhabiting North America; in size, these impressions 

 range from the prints made by tiny creatures, no 

 larger than a sparrow, to monsters which left tracks 

 each eighteen inches long. From the diversity in 

 form of the tracks it is obvious that a very large 

 variety of animals must have made them. Yet of all 

 this host, bones of only two or three have been found, 

 in localities scattered from Pennsylvania to Massa- 

 chusetts and, when it is remembered that these 

 rocks are quarried very extensively for building stone, 



1 Origin of Species, 6th Ed., London, 1872, p. 289. 



