50 THE AMERICAN MONTHLY [Feb 



America must, however, have been of a more or less 

 saline water." He thinks this is indicated by the Bacil- 

 laria found in it by Wolle. But the forms I have found 

 in it are all fresh-water forms, and certain forms which 

 Wolle found may also be fresh, as I will indicate. The 

 chalk of the Cretaceous is marine or salt-water along the 

 shore as is shown by its containing coccoliths and rhabdo- 

 liths which problematical marine organisms are not ani- 

 mal and not vegetables. They are seen now living in 

 shallow marine water and the Loup Fork marl has been 

 submitted to an Eastern zoologist who found these or- 

 ganisms in it. This, Prof. Cragin thinks may be a mis- 

 take, but it can hardly have been so. The sample may 

 have come from the Loup For 1 and may have contained 

 coccoliths and rhabdospheres and yet not have been 

 marine at all. For reckoning on the salt or fresh-water 

 origin of a sample from the microscopic organisms found 

 in it is very unreliable. In the lacustrine time, which 

 these marls are thought to represent of Plantanus, a 

 land tree, and Planorbis, Sphaerium and crushed speci- 

 mens of an Anodonta or Unio, fresh-water mollusca which 

 now inhabit shallow streams, and scales and spines of 

 percoid fishes which grow in shallow brooks also. In 

 fact, it was fresh and afterwards brackish and then dried 

 up entirely. Prof. Cragin thinks it was a large lake then 

 which he calls Loup Fork Lake. This was after the time 

 of the Occidental Sea. One part of the Loup Fork Lake 

 was brackish, very brackish, salt, and Bacillaria lived in 

 that which held salt water forms. 



The specimen I have is extremly interesting, being of 

 a light cream color. When examined by means of the 

 microscope, it is found to be made up of semi-crystaline 

 particles having a few fresh-water forms of Bacillaria or 

 Diatoms mixed with it, for I call Diatoms the dead lorica 

 or shells of Bacillaria (DiatomaceaB). When treated with 

 acids it effervesces and almost all dissolves, a few Diatoms 



