252 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
It is only some twenty years since it became known that there is in 
the United States more than one kind of “Trenton.” Naturally, 
the history of the attempts to correlate the various kinds of “Trenton ”’ 
has been made in that time. The most troublesome of the still 
unsolved problems is the exact relation of the “’Trenton” (Rysedorph, 
Chambersburg, Quebec City, Chickamauga, Sevier, etc.) of the Appa- 
lachians to the “'Trenton”’ (typical Trenton of New York, Trenton of 
Ontario, Minnesota, etc.) of the interior. 
The Appalachian Trenton, if I may so call it, extends from the 
destroyed end of the range at Gaspé in intermittent aligned exposures 
as far as Georgia. A beginning on the description of its fauna was 
made by Ruedemann (114) in his paper on the fossils in the pebbles of 
the Rysedorph conglomerate, but practically nothing more has been 
done along that line. Until the fauna is described the problem will 
remain unsolved. We have, however, some inkling of what the fauna 
is like, and notice that while in general similar to the Trenton faunas 
of the interior, it differs in containing Echinosphaerites, Christiania, 
Nidulites, Tretaspis, and Lonchodomas in abundance, these genera 
being unknown in the interior Trenton. Many undescribed forms are 
also peculiar to this Appalachian area, but the above familiar genera 
are sufficiently striking. An entering wedge in the solution of the 
problem has been driven home by the demonstration that the principal 
zone of Echinosphaerites is, over wide areas, resting upon the Leray- 
Black River. Here there is then a point of contact between the 
Appalachian and interior provinces. Dr. Ulrich will agree to this, 
but will include practically all of the limestone at Chambersburg, 
for instance, with the Nidulites, Christiania, and Upper Echinosphae- 
rites zones, in the Black River. To show that they represent the 
Trenton is a difficult, perhaps at present, impossible task, but I shall 
endeavor to present my reasons for so regarding them. ‘To do this, 
I must start with the section in New York and proceed by a round- 
about western route to reach eastern Pennyslvania. 
TRENTON IN NEw YORK. 
The type-locality is in New York State, at Trenton Falls. The 
section at Trenton Falls is unsatisfactory, in that the formation is 
not there exposed to a low enough level to show the formation upon 
which the Trenton rests. But a few miles east of Trenton Falls, at 
Rathbone Brook, is another section which supplements the one at 
