412 
PALEONTOLOGY OF NEW YORK. 
aperture; but there are indications in the striae of an obscure sinus on each 
side, half way from the centre to the lateral margins on the ventral face of 
the shell. 
The specimen described has a length of about seventy mm., and includes 
several imperfectly preserved air-chambers. Of this length, fifty-five mm. 
pertain to the grand chamber, which is equal to the greatest transverse 
diameter. The dorso-ventral diameter of twenty-eight mm. is somewhat 
reduced from the natural proportions by pressure; while the transverse 
diameter is slightly increased from the same cause. 
With only a single imperfect specimen, the determination is quite unsatis¬ 
factory ; but this form possesses so many characters in common with N. Urdus 
that its specific relations may be inferred, the features being those which 
might be presented in the immature condition of that species. 
Formdion and locality. In the arenaceous beds of the Hamilton group, in 
Madison county, N. Y. 
Nautilus bucinum. 
PLATES LX, FIGS. 1-4; CVI, FIGS. 4-7; CVII, FIGS. 2-5; CIX, FIGS. 1, 2. 
Nautilus bucinum, Hall. Illustrations of Devonian Fossils : Cephalopoda, pi. 60, figs. 1-4. 1876. 
Compare Gyroceras expansum, Saemann. Dunker and von Meyer’s Palseontographiea. 1853. 
Not Nautilus expansum, Sowerby. Min. Concho!., vol. 5, p. 83, tab. 458, fig. 1. 1825. 
Gyroceras expansum, var., Hall. Thirteenth Rep. N. Y% State Cab. Nat. Hist., p. 104. 1860. 
Shell subovoid, ventricose, rapidly expanding toward the aperture. 
Yolutions about one' and a half or two, contiguous, not embracing, 
exposed for their entire length. Umbilicus large, profound. Transverse 
section broadly elliptical. The dorso-ve'ntral and transverse diameters about 
as three to four, three to five, and five to seven, measured on different parts 
of the chambered portion of the shell, some variation being due to pressure. 
•The enlargement of the volutions is very rapid, the transverse diameter 
increasing to nearly double in less than a single volution preceding the 
grand chamber. 
Chamber of habitation large, rapidly expanding from its base, and becom¬ 
ing very ventricose. Longer than wide. Its capacity about twice as great 
