468 
PALAEONTOLOGY OF NEW YORK. 
Septa thin, somewhat regular in their arrangement; the margins moder¬ 
ately thickened, and slightly imbricating; distant from each other, at their 
origin on the umbilical side, from three to five mm. in the last fourth of 
the outer volution, the last two being closer than any of the preceding. 
From the umbilical side the septa proceed in a generally transverse direction, 
making several abrupt curves, the posterior ones of which are angular, and 
describing four saddles, of gradually increasing height and dimensions, and 
three shallow, angular lobes on the inner half of the width of the volution: 
on the outer half of the volution there are deeper and more abrupt curves; 
and leaving the base of an angular lobe at about the centre, the septa describe 
a wider semi-elliptical saddle, a deeper elongate subangular lobe, and a 
still more elongate and more elevated saddle, which has its apex near the 
periphery. On the outside of this there is a narrow lobe, and an abrupt 
turn of the septum’ to the periphery, upon which its course has not been 
observed. This arrangement gives six lobes on the lateral face of the volu¬ 
tion, each one of which has an increasing depth from the umbilical margin. 
There are likewise six saddles, each successive one of which is higher and 
wider than the preceding, except the last which is much higher, but not 
quite so wide as the one preceding it. Suture-lines narrow, moderately 
impressed upon the cast, and more strongly marked at and near the extremi¬ 
ties of the lobes and saddles. Siphuncle unknown. ' 
Test entirely unknown. The surface-markings cannot be satisfactorily 
determined on the cast of the interior or upon the weathered impression of 
the exterior, which are the only portions preserved. 
The cast of the interior is marked by nodulose annulations, which are 
nearly continuous on the inner half of the volution, and interrupted on the 
outer half: the median line of the volution being marked by a row of 
depressed nodes, which become obsolete toward and upon the chamber of 
habitation. The intermediate spaces are essentially smooth, or marked only 
by a peculiar pitted or indented surface, which has not been identified with 
any external marking. The fossil has had a lateral diameter of nearly 
eighty mm., and perhaps more than that in its entire condition. 
