4'J'J VALMOSTOLOQY OF NEW YORK. 



Formation and localities. The specimens of this form have been princi- 

 pally obtained from the Marcellus shale, at Richmondville, Schoharie county. 

 Some fragments of the same have been found at another locality in the same 

 county. 



Nautilus magister, n. sp. 



PLATES LXII, CVII, FIGS, i, 6, 7, 8 ; CVIII, FIGS. 1, 2. 



Nautilus Barrandi, Hall. Illustrations of Devonian Fossils: Cephalopoda, pi 62, fig. 1 ; pi 03, fig-. 1 ; 



pi. 64 A, tig. 2. 1876. 

 Not X. Barrandei, \ on Haiku. Haidinger: NaturwiflBenwchaftliche Abhaadlnngen, 8. Band, pL 1. 1850. 



Shell large, globose, the transverse and ventro-dorsal diameters being about as 

 eleven to twelve, making about three volutions. Volutions re-entrant, 

 embracing to one-third the diameter of the inner contiguous volution. 

 Umbilicus comparatively narrow and profound. Transverse section elliptical, 

 with a broad rounded sinus on the concave dorsal side. Transverse diameter 

 the longer, — the two diameters being in the ratio of three to four. Tube 

 rapidly enlarging. Apical angle about 18°. 



Chamber of habitation large, very ventricose, its capacity greater than 

 the entire septate portion of the shell. The length, as compared with the 

 greatest diameter at the base, is about as nine to seven, and somewhat rap- 

 idly expanding to the aperture. Aperture opening at right angles to the 

 axis of the tube, with a gentle sinus in the centre of the convex ventral 

 side. Air-chambers regular, and gradually enlarging toward the chamber 

 of habitation, the last one being shallower than the preceding; having a 

 depth of from eighteen to thirty mm. in the distance of eleven chambers, 

 as exposed on the ventral side of the outer volution. 



Septa thin, regular, very concave ; concavity greater than the depth of the 

 air-chambers; from three to four in the space of seventy-five mm., measured 

 on the convex side of the outer volution of the shell, the distance on the 

 umbilical margin being from seven to nine or ten mm. in the distance of 

 eight Bepta. The margins are extremely advanced and highly imbricate on 

 the ventral side. Their convexity in the transverse diameter is equal to 

 106°, and in the direction of the ventro-dorsal diameter 110°. Some speci- 



