37 



Surface marked near the middle of the volution by a some- 

 what broad band, the margins of which are prominent; the 

 upper part of the volutions are marked by fine transverse 

 striae, which are directed gently backwards from the suture to 

 the revolving band. 



This species very closely resembles specimens of the M. 

 Logani of the Gait limestone of Canada West, but the volu- 

 tions of that species are more ventricose, and the spire more 

 rapidly ascending. 



Geological Formation and Locality. In limestone of the age 

 of the Niagara group, at Racine, Wisconsin. 



Collector. T. J. Hale. 



Dedicated to Mr. I. A. Lapham, of Milwaukee. 



GENUS MACLUREA, Leseueuu. 



MACLUREA bigsbyi, (n. s.) 



Description. Shell thin, of medium size, discoid, consisting 

 of about four vohftions, with the umbilical (flat) side very 

 slightly depressed in the middle, and having the outer margin 

 of each volution slightly elevated above the inner or umbilical 

 margin, which, although attached to the preceding one a little 

 below the angle, gives a depression to the centre of the plane 

 by reason of the greater breadth of the outer volution. Upper 

 side very convex, giving an almost hemispherical outline to 

 this side, with a rather broad umbilical cavity, the upper mar- 

 gins of which are rounded. 



Surface marked on the periphery by strong revolving striae, 

 and on the convex side by strong, closely arranged and but 

 little elevated striae. Diameter one to two inches. 



This species differs from the M. magna, of the Chazy lime- 

 stone, in its greater depth and the more ventricose volutions. 

 From M. Logani, of Salter Canadian Organic Remains, Dec. 

 I, vol. 1, it diifers in the less rapidly increasing volutions. 



Geological Formation and Locality. In limestone of the 

 Trenton limestone group, (Buff limestone), at Mineral Point, 

 Fulton and Janesville, Wisconsin. 



Collector. T. J. Hale, James Hall. 



GENUS ECCULIOMPHALUS, Portlock. 



ECCULIOMPHALUS undulatus, (n. s.) 



Description. Shell consisting of one or two volutions, spi- 

 rally coiled, but distantly separated from each other, rapidly 

 increasing in size from the apex, and of a sub-triangular or 



