CEPHALOPODA. 
DESCRIPTIONS OF SPECIES. 
Note.— The following desci'iptions and accompanying plates are supplementary to the fossil cephalojioda 
presented in Volume V, part II, of the Palseontology of New York. After the completion of that volume, 
there still remained in the possession of the author, some new or undescrihed material, and a number of 
specimens which were important as illustrating additional features of some of the previously established 
fol’ms. The descriptions of a number of the species presented on the supplementary plates, were prepared 
in time to be included in their proper place in the volume. Such species are here merely cited, and referred 
to volume v, part 2. It has been necessary to restrict the length of the descriptions here given, on account 
of the contract limitations for the present volume. 
At the close of Volume V, part ii, in 1879, the Cephalopoda were com¬ 
mitted to the charge of Mr. C. E. Beecher, who has furnished the following 
descriptions; 
OBTHOCERAS, Breynius. 1732. 
Orthoceras duramen. 
PLATE CXVII, FIG. 1. 
Orthoceras duramen, Hall. Fifth Ann. Kept. State Geologist. Expl. pi. (117) 1, tig. 1. 1886. 
Shell straight, robust, rapidly enlarging to the chamber of habitation. Apical 
angle ten degrees. The specimen described is a compressed septate frag¬ 
ment, and the true form of the transverse section cannot be ascertained. 
Initial extremity unknown. 
Air-chambers 15 to 20 mm. in depth. 
Septa thin, deeply concave. Sutures straight, marked on the internal 
mould by narrow depressed zones, as in 0. cingulum (Pal. N. Y., vol. v, pt. 2, 
p. 240). 
Siphuncle and test not observed. 
