420 PALEONTOLOGY OF NEW YORK. 



This species is closely allied to N. oriens, which presents a somewhat different 

 surface-marking, with a closer coiling of the volutions, giving the appearance 

 M it' partially embraced by the outer volution. All the forms which have been 

 referred to that species are laterally compressed, which may cause or augment 

 this appearance. 



The N. maximus differs from N. magister in the more circular transverse sec- 

 tion, in the less closely coiled volutions, and in the surface-markings, as well as 

 in the position of the siphuncle. 



Formation and localities. In the low r er, arenaceous shales of the Hamilton 

 group, at Earlville, Solsville and other places in Madison county; and in the 

 higher shale's of the group, near Borodino, on Skaneateles lake. 



Nautilus oriens. 



PLATES LXI ; CV, FIG. 2 ; CVI, FIG. 8. 



Nautilus oriens. Hall. Illustrations of Devonian Fossils : Cephalopoda, pi. 61, fig 1 . 1. 1876. 

 Compare XtmtVnx uiarimiis (Coxr.), Hall. Page 418, plates LXI1I and LXIV. 



Shell large, subovoid, discoid, making about three volutions, which are slightly 

 re-entrant. Umbilicus very wide, exposing all the volutions. Transverse 

 section subcircular. Tube somewhat gradually enlarging in the inner volu- 

 tions. The apical angle, as taken from a compressed specimen, is about 15°. 



Chamber of habitation large, ventricose, rapidly expanding. Aperture 

 opening at right angles to the axis of the tube, with a gentle sinus on each 

 side of the convex ventral face of the shell. Air-chambers regular, deep, 

 increasing in depth with the enlargement of the volutions. The measure- 

 ment of two specimens give a depth of twenty to twenty-five mm. 



Septa regular, distant, having a greater concavity than the depth of the 

 air-chambers, strongly imbricating. As measured on the ventrum of one 

 specimen, they have a distance of twenty-five mm., where the tube has a 

 diameter of seventy-five mm. Suture lines strongly marked on the casts 

 and partial casts of the interior. 



Test imperfectly preserved, and its thickness not determined. In the 

 compressed and macerated specimens, partially retaining the shell, or its 



