CEPHALOPODA. 4G7 



preservation, with the septa obscure, it bears much resemblance to G. sinuosus, 

 but may be distinguished by the outer volution overlapping the inner ones to 

 a greater proportionate width, and a comparatively greater expansion of the 

 chamber of habitation. It is readily distinguished from all the other species 

 known to us in the New York formations. 



Formations and localities. This species is known in the shales of the Portage 

 group, on Patersou's creek, near Moscow, N. Y.; at Gibson's Mill, near the 

 Genesee river, above Mount Morris ; and above the lower Portage Falls, near 

 Portageville. It also occurs in the lower part of the Chemung group, at Pine 

 Valley, in the town of Catharine, Schuyler county, N. Y. 



GONIATITES CHEMUNGENSIS. 



PLATES LUX, flO. 9; I.XXIV, FIG. 6. 



ChniatUes Ctiemungensis. Vanuxem. Geolog. Surv. of N. Y. : Rep. Third Dist., p. 182, fig. 1. 1842. 



" " " Hall: Illustrations of Devon. Fossils: Cephalopoda, pi. 69,fig.9. 1876. 



Shell discoid, expanded. Inferring from the condition of the compressed speci- 

 men, the transverse section of the tube has not exceeded one-fourth that of 

 its lateral diameter. 



Volutions gradually expanding, about four (or five?); all exposed in the 

 wide, shallow umbilicus ; the inner ones partially embraced in the outer. 

 The transverse section is broadly oval, and a little sinuate, or somewhat 

 expanded in the middle of the sides of the outer one; rounded upon the 

 periphery, and concave on the umbilical side. The enlargement of the 

 volutions is very gradual ; the base of the air-chamber, at the end of about 

 the fourth volution, measures a little more than thirty mm. The inner 

 volutions are not in a condition to be measured. 



The chamber of habitation, known only at its commencement, is continued 

 in the same proportions as the preceding chambered portion of the shell. 

 Aperture unknown. Air-chambers numerous; the width of the volution 

 is equal to about three chambers in their greatest depth, and nearly twice as 

 many at the umbilical margin. 



