46" 
CONTRIBUTIONS TO DEVONIAN PALEONTOLOGY. 
[BULL. 244. 
tional point of view the evidence favors the hypothesis that the waters 
which produced the erosion entered through the outcrops of the porous 
sandstone zone, and, percolating downward, took out the calcareous 
portion of the rocks unevenly, the sandstones settling as erosion pro- 
ceeded; the amount of erosion being determined, partly at least, by 
the arenaceous admixture with the limestone. The irregular thickness 
was probably determined by the local position of the rocks relative tol 
flowage of water through them. 
In the more southern exposures erosion has been greater than in 
Maryland, northern Virginia, and West Virginia. The association of 
the iron ores with the sandstone portion of the formation may also be 
accounted for by the inwash of ferruginous waters into the cavernous 
interior from the surface, after the underground erosion had taken 
place. This interpretation is further borne out by the paleontological 
evidence. 
THE REISTSSEI^ERIA FAUNA. 
By H. S. Williams. 
In the following table the species from each of the zones immedi- 
ately underlying the black shale are tabulated. Twelve faunules are. 
listed, and they are arranged approximately in their order from south 
to north. They are listed together on account of their evident fauna i 
association, and because they are not separable on formational lines; 
that is, species which in the more northern sections are strictly asso- 
ciated with the calcareous and lower members of the series are, in the 
southern sections, included in the sandy beds. They may have been 
arenaceous beds which originally were calcareous sandstone, out of 
which the calcareous material has been leached by percolating waters 
after the edges of the beds were exposed to the surface drainage. The 
fauna is called in this paper the Rensseleeria fauna, and includes 
species which have been referred to the Lower Helderberg and 
Oriskany formations as they were originally denned in the New York j 
reports. 
The Rensselseria fauna of the Appalachians. 
[a, abundant 
; c, common; r, 
rare; 
L, Lower Helderberg; 0, Oriskany.] 
Sections. 
Range in 
New- 
York 
forma- 
tions. 
1376. 
1379. 
1380. 1 1382. 
1384. 
Al. 
A2. 
B2. 
C. 
E. 
Al. 
X. 
A2. Bl. 
B2. 
Al. 
A2. 
r 
r 
r 
r 
r 
r 
r 
r 
r 
6. F. cf. Cladoporasp 
7. Aulopora sp 
r 
