NOTES ON AMERICAN PALEOZOIC CEPHALOPODS 
Aug. F. Foerste 
INTRODUCTION 
The writer has been engaged for a number of years on an in- 
tensive study of Ordovician and Silurian cephalopods with special 
reference to those of American origin. The study is far from com- 
plete. A large quantity of the available material has not yet been 
examined, and some of that already studied must be re-examined 
in the light of later observations. Research of this sort is greatly 
expedited by the helpful criticism of others interested in the 
same field; but in the absence of published reports of progress, 
such assistance is limited to that secured at occasional meetings. 
Moreover, it is desirable to reduce to printed form some of the 
results thus far obtained, in order that they may be available for 
use in other studies. The following notes are accordingly a mis- 
cellaneous gathering, in part intended to invite criticism, and in 
part intended to report progress, especially along the line of 
generic relations. 
The conclusion has been reached that Ozarkian and Canadian 
cephalopods were largely holochoanitic in structure and that the 
first ellipochoanoidal cephalopods were of Chazyan age. In holo- 
choanoidal cephalopods the septal necks extend downward so that 
each is in contact with the upper margin of the neck beneath, into 
which it invaginates without connecting ring or sheath. The 
septal necks of ellipochoanoidal cephalopods are short, and suc- 
cessive necks are connected by ring-like segments, called con- 
necting rings or sheaths. Frequently these connecting rings 
have failed of preservation and then only the unconnected septal 
necks may be seen. In other specimens, especially those of Acti- 
noceroids, the septa likewise are wanting, but the siphuncle re- 
mains, reinforced by interior calcareous deposits. 
Certain species of cephalopods almost or quite invariably lack 
all trace of connecting rings. Probably in these species the mem- 
brane which ordinarily secreted the calcareous material either 
formed only a very thin deposit or none at all. 
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