PALAEONTOLOGY OF NEW YORK. 
43 8 
to twelve in the chambered portion, and about as twelye to fifteen at the 
aperture. Many specimens, in their greatest extent, have a diameter of 150 
to 200 mm.; one specimen has a diameter of over 300 mm., with the 
periphery of the chambered portion measuring about the same, and the 
periphery of its incomplete grand chamber 500 mm. A specimen, measur¬ 
ing over 200 mm. in its lateral diameter, has a transverse diameter at the 
aperture of 80 mm.; the lateral diameter of the same specimen at the last 
air-chamber being about seventy-three mm.; with the thickness of the 
shell added, the diameter would be about 75-77 mm. at this point. 
This species is very closely allied to G. Bohemicus, Barrande, and presents 
even a greater variety in the modifications of its form and surface characters. 
It attains a larger size than the Bohemian species, and the last volution is more 
rapidly expanding. 
With a single exception this is the earliest appearance of the Goniatitic type 
in our strata, and its modifications of exterior form and its great expansion in 
size are truly remarkable. Its associations and the surrounding physical con¬ 
ditions mark an epoch of sudden change in the geological history, of which we 
have no parallel in the preceding record, andscarcely one of equal magnitude 
or degree in the entire palteozoic series. Its parallel in physical conditions 
and the aspect of the fauna are only to be found in the deposits of the carbon¬ 
iferous seas. 
Formation and localities. In the Goniatite limestone of the Marcellus shale, 
at Schoharie, Cherry Valley, and near Manlius and Marcellus, in Onondaga 
county, N. Y. 
Goniatites unilobatus. 
PLATES LXXI, FIGS. 15, 16; LXXIV, FIG. 5. 
Goniatites unilobatus. Hall. Descriptions of New Species of Goniatidse, p. 1. May, 1874. 
“ “ “ Twenty-seventh Rep. N. Y. State Mus. Nat. Hist., p. 133. 1875. 
“ “ “ Illustrations of Devonian Fossils: Cephalopoda, pi. 71. 1876. 
Compare Goniatites Vanuxemi, in the preceding- descriptions and following illustrations. 
Shell discoid, the sides flattened, and joining the periphery at an obtuse angle. 
Periphery somewhat flattened; the proportions of the thickness and diameter 
of the disc not ascertained. 
