CRETACEOUS ERA. 149 



lizards, and turtles are represented by several genera ; but 

 on the whole the meridian of reptilian life is past, and the 

 huge and varied forms of the oolite are now extinct, or 

 rapidly disappearing. Of birds and mammals the highly 

 marine beds of the chalk have yielded little more than 

 the merest indications (cimoliornis, bird-of-the-chalk-marl, 

 &c. ), but as these seem to point to the higher types of the 

 rapacious birds and true mammals, we may rest assured of 

 the existence of intervening orders, and look forward with 

 hope to the discovery of their remains. 



"With the Chalk, which closes the long and prolific line 

 of mesozoic life, we lose sight of many tribes, and families, 

 and genera, but not, as is sometimes sweepingly asserted, 

 of every species that up to that time had given character 

 to the onward phases of vitality. The passage from the 

 mesozoic to the cainozoic was as gradual as that from the 

 palaeozoic to the mesozoic, and if a break shall appear to 

 exist in some districts, we cannot accept this as more than 

 a mere local and limited phenomenon. The submergence 

 of old lands, and the elevation of the sea-bed into new 

 islands and continents, is a slow and gradual process ; it 

 is never cataclysmal save over the most partial and isolated 

 tracts ; and only in such tracts is there a chance of any 

 genus or species being suddenly extinguished. As the 

 gift of life is handed from generation to generation within 

 certain limits of variety, so epoch passes it on to epoch 

 within the wider limit of specific change, but this so im- 

 perceptibly that it is only after the lapse of ages the dif- 

 ference becomes apparent. Viewed at these wide intervals, 

 the palseozoic flora seems essentially exogenous ; endogens 

 and gymnogens prevail in the mesozoic ; and now the 

 cainozoic is about to be characterised by the newer and 

 higher manifestations of the exogens. In like manner 



K 



