CEPHALOPODA OF THE CRETACEOUS MARLS. 251 
compressed discoidal, with a proportionally small umbilicus, the volutions 
have been sharp on the dorsal edge and marked by a series of undulations 
which gave rise to the specific name. The sides are ornamented by two 
lines of nodes which divide the surface into three nearly equal spaces, also 
by transverse ridges which are low and rounded, and pass from the margin 
of the umbilicus almost directly across the volution to a node one-third of 
its breadth from the margin, and are then bent sharply forward, their con- 
vexity giving rise to the undulations on the dorsal carination. Some of 
the ridges bifurcate at the inner line of nodes, each branch reaching the 
margin as independent ridges, but the fragment is too small to show how 
frequently this feature occurs. 
The septa of this specimen from New Jersey appear to be as nearly 
like that figured by Dr. Roemer, above cited, as could be expected in any two 
individuals from the same locality, consisting of a proportionally large 
dorsal lobe and three lateral lobes, visible on the side of the volution, with 
another just within the limits of or on the side of the umbilicus. The dorsal 
lobe has the main divisions bifurcating, forming two nearly equal branches, 
with numerous slender digitations ; the other is single, slender, elongate, and 
with five or six digitations. The first lateral lobe is large and somewhat 
complicated, having five principal divisions with numerous digitations. The 
other lobes are much smaller and less complicated, but all have slender, 
narrow digitations. Between the dorsal and first lateral lobe there is a long 
slender intermediate lobe with three to five digitations on a side. The 
sinuses are less complicated than the lobe, and have the terminations usu- 
ally rounded, while those of the digitations of the lobes are usually sharply 
pointed and narrow. 
The specimen bears no evidence of the siphon. 
Formation and locality: The specimen, which is a small fragment only 
of a single volution, is entirely a cast in a hard ferruginous sandy clay, 
with a few grains of glauconite scattered through it, and may have come 
from the white limetone nodules near the base of the Lower Green Marls, 
at Holmdel, Marlboro, or some of the other outcrops of this material 
within the State. As it is the only fragment of the species yet noticed, 
there may be some question as to its locality until others are fi yund. 
