Dual Character of the Kinder hook Fauna. 171 
ical age became a problem yet to be solved. The few fossils 
known from the limestone itself have been rarely met with. 
It is not at all unlikely that the lower limestone of the Kin- 
kerhook may prove eventually to be of Devonian age. But 
until abundant evidence to this etfect is found, it seems 
advisable to still consider the Louisiana (Lithographic) lime- 
stone as the basal member of the Carboniferous." 
The fact that the correlations of the Kinderhook have been 
so widely variant and as later Avork has clearly shown, in 
large part erroneous, must be ascribed mainly to insuffi- 
cient exact data, since nowhere, as it now appears, have 
investigations been detailed enough, in the attempts to solve 
the problem, to enable the critical evidence to be formulated. 
The beds of the uncertain zone have been placed first in one 
system and then in the other, sometimes witii a loss of some of 
its layers in the process of the shifting, and sometimes with a 
gain of others. These strata of undeterminate age may be 
regarded as including all those lying between the base of the 
Burlington limestone and the strata which are commonly put 
down as the western representatives of the New York Hamil- 
ton. Although these beds were originall}^ placed in the C'ar- 
boniferous, then assigned altogether to the Devonian, and 
again transferred to the Carboniferous, where they have by 
common consent and in the absence of further direct inquiry 
long remained, the accumulating evidence now points to their 
proper place in part back in the older of the two systems and 
in part in the j^ounger. However, grounds for this return in 
large part to the earliest definitely expressed view are very 
different from those which were adopted in the beginning. 
Singularly enough while the reasons for their early reference 
to the Devonian w^ere found of late years to be entirely erro- 
neous, the first conclusions were practically correct, in fact, 
for the particular district under consideration along the Mis- 
sissippi river; the premises were totally wrong, and the decis- 
ions were founded upon faulty correlations. Herein lies the 
confusion which has so long existed regarding the proper po- 
sition of the beds. 
Vei-y recently the whole subject has been taken up again, 
and as a result it has been necessary to considerably modify 
the views previously expressed. A careful examination of 
