CRETACEOUS RADIOLARIA. 51 
Porifera.] 
e 
ings from the Antarctic seas. Bailey describes them from the Atlantic, Muller 
from the Mediterranean, Hiieckel from the Adriatic, Wallich from the Indian ocean, 
and Carpenter and others from deep-sea soundings of the North Atlantic. The 
siliceous shells of the Polycystinw (one of the families of the Radiolaria to which 
most of our specimens belong) accumulated in thick deposits during the latest geo- 
logical periods, and myriads of their exquisite microscopical forms are found in 
many of the strata of Sicily, Greece, Bermuda, Barbadoes, New Zealand, California, 
and Virginia, and are now noted in the Cretaceous of Minnesota, Nebraska and 
Illinois. While somewhat abundant in some of the material, which yielded a few 
good specimens, they were mostly so fragmentary that we will not attempt to 
describe or identify them, but have figured a few specimens. They occurred most 
abundantly in the Nebraska clay, but the best preserved forms were from a soft 
dark-brown shale from near Rainy lake, northeastern Minnesota, and a few fairly 
preserved specimens were secured from Calumet (Illinois) clay. © 
PoRIFERA. 
“ PLATE KE, FIGS. 17-29. . 
Sponge spicules, mostly fragmentary, were quite frequent in some of the samples 
of material from Minnesota and Nebraska, but the spiculation of the sponge varies 
so greatly in the same species and even in the same collection, that we will not 
venture to place them, but have figured a few specimens on plate HE, figs. 17-29, of 
which 24-27 are probably of fresh water and the others of marine origin, 
EcHINODERMATA. 
PLATE E, FIGS. 30-32. 
Many fragments of spines or plates, probably of Echinodermata, well known 
marine animals, were found in some of the specimens of clay from Nebraska, 
specimens of which we have figured in plate H, figs. 30-82. 
MiscELLANEOUS. 
The well-defined organisms shown on plate E, figs. 10-16, we do not recognize. 
Fig. 15 is apparently a fish’s tooth. 
In the Chicago clay there are some very curious arenaceous cases, looking 
as if at some time they had covered very minute rootlets, or other organisms, 
which had decomposed, leaving these cases, which closely resemble rhizocarps 
of the genus Aschemonella, as figured by H. B. Brady. 
