Dual Charocter of the Kinderhook Fauna. 173 
pears to be, instead of a single compact and characteristic 
group of forms, two very distinct faunas. This is nowhere 
more clearly shewn than in the locality which may be regard- 
ed as typical and in which the fauna! zones have been deter- 
mined with considerable accuracy and corroborated by evi- 
dence from other districts. Owing to the indefinite knowl- 
edge which has long existed regarding the exact horizons at 
which the various genera andspecies occur, the general faunal 
facies of the "Kinderhook" has heretofore borne a compos- 
ite and not a pure ph^^siognomy. 
A tabular arrangement of all the species of fossils that are rec- 
ognized at a typical locality of the Kinderhook, and that range 
from the Silurian to the upper Burlington, has brought out 
very clearly some important facts which have been overlooked. 
The first of these is the close affinity of the faunas from the 
lower two members of the "Kinderhook," with the underlying 
Devonian, and the second is the sharpness with which the 
lower fauna stops at the base of the Chouteau, and the abrupt- 
ness with which an entirely new fauna begins at the same 
level. 
Second. The components of the lower fauna comprise those 
forms which occur in the Louisiana limestone and the Han- 
nibal shales. As a whole the fauna is evidently closely re- 
lated to that occurring in the western Hamilton. Some of the 
species, though bearing different names, are in reality identi- 
cal with typical forms of that formation. As already stated 
the fossils have been found, with few exceptions perhaps, 
only at the basal portion of what is called the Louisiana 
limestone, in a thin sandy layer which is lithologically simi- 
lar to the partings in the limestone itself. The results of the 
latest investigations show that many of the forms actually 
extend upwards, some of them being practically unchanged 
through the whole Louisiana to the top of the Hannibal. 
Thus far not a single species of this fauna appears to occur 
higher, or in the overlying Chouteau. Many of the forms also 
range downwards into the dark colored shale below, which is 
regarded as of Devonian age. 
The general impression derived from a tabular arrangement 
of all the species is that the lower zones, forming the Louis- 
iana, the commonly accepted base of the Carboniferous, are 
