408 
PA L2EON TO LOGY OF NEW YORK. 
portions. Near the apex they are distant from each other less than two mm., 
and diverge until they are at least ten mm. distant toward the aperture. The 
interspaces are at first curved in the bottom, concave, becoming gradually 
flattened, as the distance between the ridges increases. The entire surface 
is marked with fine, thread-like, transverse striae; and sometimes, in the 
exfoliated condition, with obscure, revolving striae, which appear to pertain 
to the inner or nacreous layers of the shell. 
The internal cast is distinctly marked by the suture lines, and by the 
strong revolving ridges; and obscurely marked by the transverse and revolv¬ 
ing striae. One specimen has a diameter of ninety mm., and includes a por¬ 
tion of the grand chamber, occupying about half a volution. A fragment of 
the chambered portion, incomplete at the apex, measures 130 mm. on the 
periphery. 
The typical specimen preserves a mammillary deposit upon the surface, 
apparently connected with the inner laminae of the shell. 
This species is quite distinct from the ordinary forms of Nautilus, and there 
is little external similarity between them. It is referred to Nautilus on 
account of the contiguous volutions, the form of the transverse section, the 
large, apical angle, the comparative size of the chamber of habitation and the 
chambered portion of the shell, and the absence of any well-defined sinus, while 
the siphuncle.is subcentral. This species is distinguished from the other forms, 
except N. subliratus, by the presence of strong, revolving carinae. 
In the typical specimen of N. liratus there are fourteen revolving ridges over 
the chambered portion of the shell, a part of which become obsolete upon the 
ventral side of the grand chamber. In the specimen fig. 3 of plate 57 there are 
nine strong plications seen on the lateral face of a partially compressed grand 
chamber. 
Formations and localities. In the Goniatite limestone, near Manlius, N. Y.; 
and in the shales of the Hamilton group, in Madison county. 
