260 PALEONTOLOGY OF NEW JEKSEY. 



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 Fig. Ic, 

 PI. XXXIV, 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 lobfes 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. S. Cook, Esq., near Tinton Falls, New Jersey, 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 MoUuscan remains of the Middle Marls, in a 

 yellowish green marl sand, which appears to be peculiar to that horizon, if 

 not to that locality. 



