350 EIGHTEENTH REPORT ON THE STATE CABINET. 



GENUS ONCOCERAS (Hall). 



ONCOCEKAS OECAS. 



Cyrtoceras orcas : Report of Progress Geol. Survey of "Wisconsin, 1860-1, p. 42. 



This species should properly be referred to the Grenus Oncoceras, of 

 which it is the only representative at present known to me in this forma- 

 tion in Wisconsin. 



GENUS GOMPHOCERAS (Sowerby). 



GOMPHOCERAS SEPTORIS (n. s.) 

 The outer chamber of a Gomphoceras, including the first septum, shows 

 a submarginal siphuncle, with broad subelliptical section. The lateral aper- 

 ture extends to a point nearly half way from the apex to the first septum, 

 and is continued in a narrow constriction nearly to the apex, where it is 

 united with the larger aperture : the margin of this is contracted into 

 tubular folds, so narrow as to present the appearance of three small 

 rounded lateral apertures, with a similar one on the dorsal side. 



This peculiarity of the aperture is sufiicient for specific determination, 



when compared with any species known to me. 



9 10 



Fig. 9. Gomphoceras septoris ( Lateral view of the outer chamber). 

 Fig. 10. *•' '' (Showing the form of the aperture). 



Formation and locality. In limestone of the Niagara group, at Wau- 



watosa, Wisconsin. Dr. H. Day. 



GOMPHOCERAS SCRINIUM ( n. s.). 



A specimen consisting of the outer chamber and first septum, is of 

 moderate size, transversely subcircular, with a very slight angularity on 

 the ventral side. Outer chamber rapidly contracting from near the last 

 septum to the aperture, giving it a somewhat conical form, the length 

 being less than the transverse diameter of the septum. Aperture trilobed, 

 the ventral opening small ; dorsal opening moderately large and subtrian- 

 gular : the proportions of the transverse and axial diameters are as three to 

 four. Septa moderately deep, with a very regular convexity. Siphuncle 

 situated at one-third the distance from the ventral margin to the centre. 



Surface marked only by irregular lines of growth. 



Formation and locality. In limestone of the Niagara group, from Illi- 

 nois ; the particular locality unknown. 

 46 



