S. W. Wallace— Geodes” of the Keokuk Formation. 369 
non-mineral substance, and many parts formed of lime, have 
first entirely disappeared, so as to leave vacant cavities. me 
of these are still vacant. But most have been afterward filled 
by crystals from water containing bicarbonate of lime and silica, 
which show no internal structure of the original body. i 
includes not only these grades, but a large proportion of the 
crinoids, skells and corals, that originally arias lind: so that 
this is not so strange for the non-mineral sponges as for those. 
The following is the principal distinct type: 
BIOPALLA (new genus). 
inches, varying from one line to over two feet; no foot-stalk 
marked peculiar cushion-like figure. 
Named from the Greek, féo¢, life, and zadda, a ball. 
There is uncertainty as to the distinction of species, but I 
venture to name the following: 
“eke very distinct, few to medium, symmetrical and regular. 
nterspaces large, swelling lobe-like. A few largest indrawn 
ion. 
Biopalla’ Wortheni—Size medium to large; form varied ; 
vertical and lateral faces different. Markings on top more or 
less sharp and crowded; on lateral sides, less numerous, and 
ehinngatol vertically ; on bottom not so sharp as on top; other- 
wise more or less varied, as in B. Keokuk. 
From Hamilton, Ill.; Drift ; and other places. 
Biopalla Woodmani.—A peculiar form from the Drift, Keo- 
kuk, Iowa, supposed to be from the northward. Found as 
