4G0 IWUEOSTOLOGY OF NEW YORK. 



GONIATITES STNUOSUS. 

 PI.ATKS LXX, FIGS. 1S-15 ; I.XX1I, KIG 11; LXXIV, FIG. 11. 



Ooniatitet *inuo*ut. Ball. Gteolog. Burv. N. V. : Rap. Fourth Dlat, p. 148, fig. 0. 1843. 



" Illustrations of Devonian Fossils : Cephalopoda, pi. 78, fig. 11. 1876. 

 " (Clymeniat) Nundaia, Hall. Descriptions of New Species Goniatidav p. 8. May, 1871. 



Twenty-seventh Sep. N. T. State Mus. Nat. Hiat., p. 184. 1878. 

 •• •' " " Illustrations Devon. Fossils|: Cephalopoda, pi. 70, figs 13-15. 1876. 



H mn.T. broadly discoid, with the sides gently curving, or sometimes nearly flat ; 

 the thickness of the disc is thirty mm. or more in old specimens where the 

 lateral diameter is about 100 mm. 



Volutions about three or four, the inner ones gradually enlarging, while 

 the outer ones expand much more rapidly and become ventricose in the 

 chamber of habitation. The outer volutions embrace the inner ones to an 

 extent of one-quarter of their diameter. Umbilicus wide, exposing all the 

 inner volutions, its margins nearly vertical, the exterior angle rounded. 

 Transverse section semi-elliptical, having a height of once and a half the 

 breadth at the base, in the outer volution ; the sides curve gently toward the 

 periphery, which is abruptly and regularly convex, having a width about half 

 as great as the base, which is two-thirds as wide as the lateral face, and slightly 

 indented by the preceding volution ; the baso-lateral angles slightly auricu- 

 late. The rate of increase, in two outer volutions of a nearly entire large 

 specimen, including more than half a volution of the chamber of habitation, 

 is from four to twelve and forty-two mm. The specimen figure 16, plate 70, 

 shows an increase in the outer volution from less than fourteen to forty- 

 five mm. 



Chamber of habitation large, occupying more than half a volution in entire 

 specimens, and having a capacity much greater than all the chambered portion 

 of the shell. Aperture semi-elliptical, with the apex somewhat truncate and 

 the sides gently expanded. The base is slightly indented by the preceding 

 volution, and the baso-lateral angles are auriculate. Air-chambers numerous, 

 somewhat irregular, and gradually increasing in depth toward the chamber 

 of habitation, except the last one or two, which are shallower than the pre- 



