45G PALJSONTOLOQY 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- 

 iii' II-, lias not been satisfactorily determined. 



