434 PAL - 1: < ' v TO LOO V OF SEW YO RK. 



more abruptly on the ventral side.- The ventral lobe extends about half 

 the depth of the adjacent air-chamber, and is abruptly narrowed below, the 

 walls being essentially parallel and coincident with those of the siphuncle. 

 The septa are thin in the centre, thickened and imbricating at the margins, 

 leaving a deeply marked suture line. 



Siphuncle unknown, except as it appears in the termination of the ventral 

 lobe in the cast. 



Test and surface-markings unknown. 



An imperfect cast of the interior measures about ninety mm. in its greatest 

 lateral diameter, with a transverse diameter of less than twenty-five mm. 



This species bears much general resemblance in form to G. discoideus, of the 

 Hamilton group, but the disposition of the septa is very distinctive. In some 

 of the characters it corresponds very nearly with G. Ixion, the lateral lobe being 

 rounded, instead of acute. The specimen is calcareous, but with the surface 

 entirely weathered. 



Formation and locality. This specimen was received from the late Dr. Mann, 

 of Delaware, 0., as coming from the Upper Helderberg limestone, in the vicinity 

 of Columbus. 



GONIATITES VaNUXEMI, n. Sp. 



PLATES LXVI-LXVUI; LXIX, FIGS. 8-6; CIX, VMM. 7, 8. 



Gunintitet expanms, Vakuxbm. 9urv. N. Y. : Rep Third Dist., p. 146, fig. 1. 1842. 



Hull: Thirteenth Rep. N. V. State Cab. Nat His!., pp. ;)i;, '.17, figs. 1.2. I860. 

 " " " Hall: Illustrations of Devonian Fossils j Cephalopoda, pis. 64 A, til! li'J. ISTli. 



Not " " von Buch. Uei>er Goniatiten and Clymenieo in Bcbleslen. Bert. AJcad. Mob., 1838. 



Berlin, 1839. 



Shbll large, discoid, flattened on the sides and upon the periphery in its 

 advanced stages of growth. Transverse diameter varying according to the 

 age of the shell, from one-half to one-third, and less than that proportion, of 

 the greatest horizontal diameter; the younger forms are much more rotund, 

 the two diameters being about as one to one and three-fourths. 



Volutions of the spire about three to four in specimens of smaller and 

 medium size, and not determined in the larger ones. Near the apex the 

 inner volutions are embraced in the succeeding ones to the depth of one-half 



