248 
PALAEONTOLOGY OF NEW YORK. 
Formation and localities. In the Schoharie grit at Schoharie, Clarksville, 
Knox, and other points in the Helderberg mountains. 
Ortiioceras oppletum, n. sp. 
[PLATES LXXXI, FIGS. 9-12; CXII, FIG. 11. 
Shell robust, straight; tube gradually enlarging. Transverse section subcircular. 
Chamber of habitation unknown. Air-chambers regular, having a depth 
of about six mm. 
Septa, and also some portions of the organic deposit, ornamented by fine, 
irregular, lainellose strim, which are sometimes concentric about different 
points on the septa and chamber-walls, generally parallel, and running in 
the direction of the longitudinal axis of the shell. 
The siplmncle is situated at about one-third the diameter of the tube from 
the ventral (?) side. Its diameter at the septa is very small. Between the 
septa the characters have not been observed. 
The organic deposit around the siphuncle is similar to that of O. luxum , 
forming a sharply furrowed cylinder between the septa—the furrows in this 
species being much larger and more irregular than in 0. luxum. The depo¬ 
sition is carried to such an extent as almost or entirely to fill the cavity of 
the chambers, as represented in fig. 12, pi. 81. The separate globular masses 
of the deposit sometimes have a diameter of six mm. Towards the cham¬ 
ber of habitation the deposit is at first a large areola, with a lamellose striate 
margin, and a fascicle of the striae extending to the margin of the septum. 
On the septa the deposit is composed of very small globular masses, and in 
appearance is similar to the same deposit in 0. luxum. 
One individual of this species has a diameter of the tube of about forty mm. 
The appearances of the internal mould are sufficiently marked to readily 
distinguish the species. The peculiarities of the organic deposit and the 
ornamentation on the septa are very characteristic. 
This species somewhat resembles 0. luxum in the amount and appearance of 
the organic deposit. It is, however, much more developed and coarser in its 
