434 
PALAEONTOLOGY OF NEW YORK. 
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 — LXVIII; LXIX, FIGS. 3-6; CIX, FIGS 7, 8. 
Goniatites expansus, Vanuxem. Geolog-. Surv. N. Y. : Rep Third Disk, p. 146, fig-. 1. 1842. 
“ “ “ Hall: Thirteenth Rep. N. Y. State Cab. Nat. Hist., pp. 96, 97, figs. 1,2. I860. 
“ “ “ Hall: Illustrations of Devonian Fossils: Cephalopoda, pis. 64 A, 66-69. 1876. 
Not “ “ von Buch. Ueber Goniatiten und Clymenien in Schlesieti. Berl. Akad. Mon., 1838. 
Berlin, 1839. 
Shell 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 
