9 
308 Cincinnati Society of Natural History. 
occurs in the Keokuk of Indiana, Illinois, and Iowa, but is more rapidly 
expanding than the form from New Mexico. This difference can 
hardly be of specific importance. 
12. Proetus peroccidens._-This species was described from the Sub- 
carboniferous of the Rocky Mountain region, and though our cae 
is quite fragmentary it probably belongs to it. 
13. Amplexus. fragilis.--This species was described from the Keokuk 
Group of Iowa, but it also occurs in the Burlington, in the same State, 
and it is common in the Keokuk of soutbern Kentucky. 
14. Cyathophyllum subcespitosum._-This species was described 
from the Carboniferous of the west, and compared with Cyatho- 
phyllum pseudo-vermiculare from the Subearboniferous of Ireland, with- 
out longitudinal sections, The differences between the species are 
not readily determinable without cut sections, and it is, therefore, a 
matter of doubt to which species our specimens belong. 
15. We have also two undetermined species of Zaphrentis, two unde- 
termined species of Bryozoa belonging to the family Menestellide, and 
the fragment of an Orthoceras. 
It is, however, the appearance of the crinoids, res than the above- 
mentioned species, that inclines us to refer the rocks to the age of 
the Burlington, instead of the Keokuk. Brachiopods and corals fre- 
quently have an extended vertical range, but crinoids are ugually 
confined to a few feet, and it is an exceedingly rare occurrence for a 
species to pass from one group to another. The separation of the 
Burlington from the Keokuk could hardly be maintained were it not 
for the great change in the character of the crinoids. Of course, in 
Towa and Missouri, a cherty layer, which Hall, in defining these groups, 
placed at the base of the Keokuk, separates them; but even here 
they are so intimately blended, that some authors refer the chert 
layers to the Upper Burlington. Without any information regarding 
the appearance of the rocks, in Lake Valley, or whether the fossils 
are all from the same elevation or not, and looking at the fossils above 
mentioned, and those hereafter to be mentioned and _ described, 
and supposing them to come from substantially the same elevation, 
we would confine the rocks between the base of the Burlington and 
top of the Keokuk, with the probabilities in favor of the age of the 
Upper Burlington. 
There are in this collection three species of Platycrinus, one of them 
truncated at the hase like P. wortheni, and another having the form of 
P. planus, though neither species is in condition to be described, and 
