CRETACEOUS FLORA. 27 



Source of Foraminifera.l 



and rhabdoliths, which largely give to the water its milky appearance, will be lost. 

 They are very fine and very light, and some of them will remain suspended in a 4 oz. 

 beaker of water for several hours. They can be separated from the other material 

 by repeated washings and decantations, so as to make almost pure mountings, but 

 the resting time between decantings must be from one-half to three-quarters of an 

 hour. 







II. FORAMINIFERA. 



This paper is the result of the preparation and microscopical examinations of 

 several hundreds of slides of material from the boulder clays, hard and soft Creta- 

 ceous shales, rotten or chalky limestone, etc., from various parts of Minnesota, many 

 samples of which were collected, as already stated, by Prof. N. H. Winchell, state 

 geologist of Minnesota ; from boulder clay and fragments of shale, kindly sent by 

 Prof. G. D. Swezey, Doan College, Nebraska, and from our own collections in Illinois 

 and Wisconsin. Much of the material examined abounded in fossil remains of 

 Foi'aminifera, radiolarians, coccoliths, rhabdoliths, fresh- water Diatomaceae, sponge 

 spicules, and other microscopical organisms ; but by far the most numerous and 

 interesting were the calcareous casts or shells of Foraminifera, a minute marine 

 animal of the sub-kingdom Protozoa, class Rhizopoda. 



These fossils in the clays are evidently derived from the Cretaceous formations 

 which have been broken up and their contents scattered through the boulder clays 

 presumably in the direction of the glacial currents. In many localities in Minnesota 

 and Nebraska, and on the upper Missouri and Niobrara rivers, the Cretaceous form- 

 ations are yet in place, and some of the chalk rocks are almost wholly composed of 

 these organisms. The "Eoliansand" of the Smoky Hill river, near Lindsborg, Kansas 

 where the river has cut its way through the Cretaceous rocks, is very rich in many 

 species of well preserved Foraminifera, and it is probably the presence of vast numbers 

 of these minute marine shells in the sand th'at gives to it its peculiar quality. The 

 same genera and species of Foraminifera that constitute so considerable a part of 

 some of these Cretaceous rocks, and that are so abundant in some of the boulder 

 clays, are now living in vast numbers in the Atlantic, Mediterranean and other 

 oceanic waters. They constitute an important ingredient of the ''chalk cliffs "of 

 England and the building stone of the city of Paris, France, is largely composed of 

 them. The "Nummulites", or "Coin-stones" of which the pyramids of Egypt are 

 built are principally Foraminifera. 



Fairly well preserved casts or shellsof Foraminifera were more or less abundant 

 in most of the specimens from Minnesota and Nebraska, and a few good forms of 



