456 
PALEONTOLOGY OF NEW YORK. 
The chamber of habitation is very deep, occupying more than half a volu¬ 
tion, and becoming moderately expanded toward the aperture. Aperture 
semi-elliptical; lateral margins but slightly curved; indented at the base by 
the preceding volution, with the baso-lateral angles slightly auriculate. The 
anterior margin, inferring from the direction of the striae, is deeply sinuate. 
Air-chambers numerous, regular, except toward the chamber of habitation, 
having a depth on the middle of the lateral face about equal to one-fifth the 
width of the volution at that point, or a depth of two mm. where the diam¬ 
eter of the tube is ten mm., and with scarcely a measurable difference where 
the tube is a millimetre more or less in diameter. 
The septa are thin and very slightly thickened at their margins. Rising 
from the axis, they make a gentle retral bend, and are recurved toward the 
aperture from a point about one-third the width of the volution from the 
umbilical margin, describing a shallow lateral lobe; thence arching more 
abruptly, they include a more elevated lateral saddle, the apex of which is at 
a point about two-thirds the width of the volution from the umbilical margin. 
From this point the septa arch backward, limiting a narrow, acute lobe on 
the peripheral margin. The course of the septa on the periphery and the 
form and character of the ventral lobe have not been determined. 
Siphuncle not observed. 
Test thin, rarely or but partially preserved in the specimens under exam¬ 
ination. Surface marked by fine, regular striae, which are curved a little 
forward from the umbilical side of the volution, and, when reaching a point 
near the periphery, or about three-fourths of the width of the volution, are 
bent backward into a shallow, undefined, revolving groove, from which they 
make an abrupt turn to the periphery. The sinus, inferring from the 
direction of the striae, is comparatively deep. 
The internal mould is smooth, except the septal indentations, and the 
impressions of the surface striae are scarcely visible The specimens have a 
prevailing lateral diameter of from thirty to forty-five mm., while the 
transverse diameter, owing to the usually flattened condition of the speci¬ 
mens, has not been satisfactorily determined. 
