454 1'AUEOXTULOQY OF NSW YORK. 



tion, becoming a little more ventricose. Aperture unknown. Transverse 

 ion of the outer chamber the same as the preceding volutions, seini- 

 ellipticul, 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. 



