CRETACEOUS RADIOLARIA. 51 



Porifeni.l 



ings from the Antarctic seas. Bailey describes them from the Atlantic, Muller 

 from the Mediterranean, Haeckel 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 Polycystince (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. 



PORIFEEA. 



PLATE E, 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 E, figs. 17-29, of 

 which 24-27 are probably of fresh water and the others of marine origin. 



ECHINODERMATA. 

 PLATE E, FIGS. 80-32. 



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 E, figs. 30-32. 



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. 



