LESSONS FROM A LUMP OF CHALK. 171 



other strata I have picked up oyster shells seven inches in 

 diameter, and nearly round. Single valves, I think weigh 

 sometimes two or. three pounds. One might have broiled oys- 

 ter steaks if he had lived in those days. The Cretaceous 

 strata seem to have been a literal oyster cemetery. 



But who, after all, would prefer to have lived in those 

 times? Even had human society been supplied, the world 

 was really not prepared for man. We do not find any bones 

 of horses or oxen, or any of our domestic and useful animals. 

 Nor do we find remains of any of our fruit-bearing trees or 

 berries of any kind. I think we should have lost more than 

 all the gain far more. Instead of relics of domestic animals, 

 we discover teeth and vertebrae of sharks of different tribes 

 some with tapering, lance-like teeth, some very long and slen- 

 der, and some flat and lying like paving stones on the bottom 

 of the mouth. Here too are the vertebrae of a long and 

 snake-like reptile known as Mosasaur. It was probably a 

 genuine "sea-serpent." The relics of these ancient popula- 

 tions are now plowed up in the cotton fields. In the region 

 south of Selma I have seen the precious relics of curious and 

 extraordinary shells, which we call Rudwtes, carted together 

 and burned for lime to whitewash log-cabins. 



From Texas, the great Cretaceous belt can be traced 

 northward to Kansas, Nebraska, Minnesota, Dakota, and 

 British America. It extends, indeed, along the east flanks of 

 the Rocky Mountains, apparently to the Arctic Ocean. 

 These are interesting facts. They demonstrate that there 

 was a time when an ocean stretched from the Gulf of Mexico, 

 through the middle of our continent, to the Arctic. These 

 Cretaceous strata contain neither chalk nor " rotten limestone." 

 They were not formed in a deep sea. There are vast forma- 

 tions of clay and shale, and at the bottom is a thick sand- 

 stone, often conglomeritic, which can be traced from Kansas 

 to the Wahsatch Mountains but not in one continuous sheet. 

 All these Cretaceous strata being formed of fragments coarse 

 or fine, are called fragmentaL Evidently they were laid down 

 in waters mostly shallow, and to a great extent, near the 



