260 PALEONTOLOGY OF NEW JERSEY. 
P. placenta. 'The principal point of difference between these species, how- 
ever, is in the form and details of the septal lines, as shown on the surface 
of the casts. On P. placenta they are much branched, both on the lobes 
and sinuses throughout, but in this form they are altogether more simple, 
the lobes having two or three obtuse points on each of the divisions, and 
the sinuses being simple for some distance from the umbilicus, then becom- 
ing biclavate and outside of the middle of the breadth of the volution often 
first irregularly triclavate, and sometimes with four clavate divisions in older 
specimens. In specimens of large size, however, from: Missouri, they are 
seldom as strongly divided as those represented by Mr. Meek in his F ig. Le, 
Pl. xxxtv, of the work just cited. In the fragments of chambers seen from 
New Jersey, although evidently from a specimen of large size, the sinuses 
appear to have been simply bilobed, the division between the lobes having 
two short points, while the lobes have the features shown in those of the 
sixth to the ninth lobes of Mr. Meek’s figures. There is no feature on the 
fragment by which I can definitely tell from what position within the breadth 
of the volution the one fragment came, so that I can only surmise as to the 
corresponding lobes of a more perfect specimen. But it is fair, probably, 
to suppose that it came from near the position above mentioned, as if not, 
or if it came from nearer the outer edge, it would indicate a different form 
from the western shells. 
Formation and locality: The only fragment I have seen comes from 
the marl pits of J. 8. Cook, Esq., near Tinton Falls, New J ersev, and are 
from the lowest layers of the Middle Marls, where they are associated with 
Nautilus Dekayi and small specimens of Baculites ovatus of the Lower Marls, 
as well as with many of the Molluscan remains of the Middle Marls, in a 
yellowish green marl sand, which appears to be peculiar to that horizon, if 
not to that locality. 
