PALEONTOLOGY 95 



of known species, and which were inhabiting the same 

 regions, were lost, while, for the^nost part, only well- 

 defined species were preserved. 



, LeConte says: "We think the fragmentariness of 

 the geological record has been overstated. While it 

 is true that there are many and wide gaps in the 

 record; while it is true, also, that even where the 

 record is continuous many forms may not have been 

 preserved, yet there are some cases, especially in the 

 Tertiary fresh-water deposits, where the record is not 

 only continuous for hundreds of feet in thickness, 

 but the abundance of life was very great, and the 

 conditions necessary for preservation exceptionally 

 good. In such cases the number of fossil species 

 found on each horizon seems to be as great as in exist- 

 ing faunas over equal space. The record in these 

 oases seems to be continuous and without break, and 

 •crowded with fossil forms; and yet, although the 

 species change greatly, and perhaps many times, in 

 passing from the lowest to the highest strata, we do 

 not usually, it must be acknowledged, find the gradual 

 transitions we would naturally expect, if the change 

 were effected by gradual transitions. The incom- 

 pleteness of the record, therefore, although a true 

 and important cause, is not the whole cause."* He 

 further speaks of the absence of connecting links as 

 ** the greatest of all objections " against the theory of 

 evolution. 



If the above case of the Fresh-water Tertiary exists 

 with rocks hundreds of feet in thickness, with abun- 

 dance of life, and exceptionally good circumstances 

 for preserving fossils, with abundance of well-defined 

 species, but with the. usual absence of intermediate 

 forms, then may it not be that a large part of the 

 geological record is destitute of the numerous breaks 

 * Evolution, p. 234. 



