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ONCOCERAS alceum, (n. s.) 



Description. Shell robust, Dearly straight or but slightly 

 arcuate, rapidly expanding from the middle of the shell and 

 and swelling out more abruptly at the distance of an inch 

 below the outer chamber, which gradually diminishes towards 

 the aperture and constricted behind the margin. Transverse 

 section elliptical, the longest diameter being as nine to twelve 

 and a half. Septa about seven or eight in' the space of an 

 mch, very slightly concave. Siphuncle large, slightly inflated 

 between the chambers, dorso-lateral or dorsal, being on the 

 margin, half way between the line of the transverse and lon- 

 gitudinal diameters. 



Some remains of strong lamellosc strise of growth are pre- 

 served on the outer chamber. Length preserved, two and a 

 'half .inches; the greatest diameter a little more than one and 

 a quarter inches. 



This species is remarkable for the straightness of the shell, 

 and the elongate-elliptical form of the section. The position 

 of the siphuncle may be considered as dorsal, it being upon 

 the outside of the curve, the inner side of the curve and great- 

 est attenuation of the septa being opposite. At first sight the 

 position of the siphuncle appears to be due to distortion, but 

 the relations of the parts have not suffered, and it does not 

 seem possible that it could have been moved by pressure with- 

 out distorting the form and proportions of the parts. 



Geological Formation and Locality. In the "Buff limestone" 

 of the Trenton limestone group, at Beloit, Wisconsin. 



ORTHOCERAS gregakium, (n. s.) 



Description, Shell of medium size, gradually expanding 

 from the apex; transverse section circular. Septa deeply 

 concave, not very distant, varying from six to nine in the 

 space of an inch, according to age. Siphuncle central in 

 young specimens, often becoming sub-central or quite excentric 

 in old individuals. 



Surface smooth except fine concentric lines of growth. 



This species somwhat resembles some specimens of 0. pro- 

 leiforme of the Trenton limestone of New York; but it differs 

 in the uniformly smaller size, greater concavity of septa, and 

 more central siphuncle; while in that species the siphuncle is 

 STtib-marginal. 



Geological Formation and Locality. Abundant in the lower 

 part of the shales above the Galena limestone; at Makoqueta 



