158 Sioujc City Academy of Science and Letters. 



This brings up to Cenozoic Time, when the mammalian 

 fauna predominated over the lower and disappearing 

 reptilian forms. Cenozoic means recent life, and this 

 time has been divided by geologists into two ages, the 

 Tertiary and Quaternary, the former the age af mam- 

 mals and the latter the age of man. All the great mam- 

 mals of the Tertiary age are extinct. They were won- 

 derful in number and variety as well as monstrous in 

 size. Nearly all the land animals, from their first ap- 

 pearance, have been vegetable feeders, and through all 

 the time they existed in their age their size increased. 

 The line of development has seemed to be, so far, in 

 bulk or bone and muscle. They were great in bodily 

 size, but had very small brains and were stupid, sluggish 

 and low in intelligence. If one will examine the cuts 

 showing the fossil skulls of these extinct monsters, which 

 are shown in Dana's Manual of Geology, the exceeding 

 smallness of brain in comparison with the size of skull 

 will be very striking. It seems as if nature, in maintain- 

 ing the harmony between being and environment, had 

 built up the body until the limit, beyond which she could 

 not go in this direction, had been reached. In our civil 

 war I well remember a case in my own regiment which 

 illustrates the difficulty with which organisms of strong 

 body are subject to in changing climate and surrounding- 

 conditions, which may make plainer some of the reasons 

 why the monstrous animal forms of the Tertiary age 

 became extinct. Among the companies in the regiment 

 to which I belonged was one from the northern part of 

 my state, Wisconsin. They had been lumbermen at 

 home, and were the finest looking lot of men in the regi- 

 ment, nearly all over six feet in height, strong and ro- 

 bust in body. But in the camps of a different climate 

 they fell far behind in health and endurance the younger 

 and more frail appearing young men of the cities. The 

 change of climate was much harder for them than for 

 those more immature in age and bodily vigor. So with 

 those great animals of Tertiary times. They could not 

 adapt themselves to the changing conditions of the phys- 

 ical environment, and so perished and became extinct. 

 Not one of those strange and uncouth shaj)ed animals 



