CRETACEOUS FLORA. 27 
Source of Foraminifera. | 
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 
Foraminifera, radiolarians, coccoliths, rhabdoliths, fresh-water Diatomacee, sponge 
spicules, and other microscopical organisms ; but by far the most numerous and 
interesting were the calcareous casts or shells of Foraminifera, a minute mariné 
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 “Kolian sand” of the Smoky Hillriver, 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 that 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 
