454 
PALEONTOLOGY OF NEW YORK. 
tion, becoming a little more ventricose. Aperture unknown. Transverse 
section of tlie outer chamber the same as the preceding volutions, semi¬ 
elliptical, with the base indented by the inclosed volution, and the baso-lateral 
angles auriculate. Air-chambers regular, gradually increasing in depth with 
the increase of the volution ; shallow on the umbilical margin, and more than 
twice as deep on the middle of the lateral face, which measures the greatest 
elevation of the lateral saddle. 
Septa moderately thick and strong, with the margins thickened and 
imbricating toward the aperture; those of the outer volution having a dis¬ 
tance from a little less to a little more than one mm. at the umbilical margin ; 
thence making a retral curve they turn forward, reaching the greatest advance 
about the middle of the lateral face; thence curving backward to near the 
ventro-lateral margin they make an acute bend forward to the margin of the 
periphery, and again gently returning to near the centre of the periphery 
they describe a short, narrow lobe upon the ventral margin. This disposition 
of the septa leaves a shallow lobe just outside of the umbilical margin, with 
a broad, elevated saddle occupying the central portion of the lateral face, a 
narrow, deep lobe near the peripheral margin, with a low, rounded saddle 
on either edge of the periphery, and a short, narrow central lobe which 
indents the adjacent air-chamber to about one-eighth of its depth, or .75 mm. 
where the chamber is five mm. in depth. In the measurements of the curves 
of the septa the width of the lateral lobe is equal to half the width of the 
saddle; the depth of the lobe is equal to half the height of the saddle 
and equal to the depth of two air-chambers. 
Test thin, not preserved upon the specimen. Surface-markings unknown. 
Sinus undetermined, but probably narrow and not deep. The shell has been 
crystallized, and inferring from some fragments remaining, it probably had a 
thickness of about one mm. The internal cast is smooth, with suture lines 
strongly impressed. 
The specimen figured, which is imperfect, has a lateral diameter of about 
forty-five mm., with a transverse diameter of about eighteen mm. Its vari¬ 
ation in dimensions and entire form are unknown. 
