New Species of Palaeozoic Fossils. 179 



Buchanan county, Iowa, and occasionally in limestone of the 

 same age at other localities in the same state. 



I know of no species with which this could be directly com- 

 pared. Euomphahis dccczvi, Billings, is a large species be- 

 longing to this same group, but S. lativolvis differs conspic- 

 uously from E. dccczvi in having fewer, broader and more 

 rapidly expanding whorls; the whorls are more symmetrical; 

 the flattening is on the upper, instead of on the low^er side of 

 the volutions, and the spire is proportionately less depressed. 

 The whole shell is thinner and more discoidal. 



Straparollus bicarinatus, n. s. 



PLATE III., FIGS. 2 a, b. 



Shell of medium size, rather large, whorls oblique, spire 

 slightly elevated; lower side with a broad and moderately 

 deep umbilicus, in which the successive volutions are each 

 about half exposed; volutions four or five, very gradually ex- 

 panding, suborbicular in cross section; periphery marked by 

 a strong carina; a second carina, less prominent, sometimes 

 almost obsolete, marks the middle of the dorsal side of each 

 volution; lower side of the volutions rounded or marked in 

 the middle line by a revolving, sub-angular ridge. On the 

 upper side the spaces between the peripheral and dorsal carinse 

 and between the dorsal carina and the suture are regularly 

 convex. Aperture nearly round, the deviation from the 

 orbicular form being due chiefly to the salient angles corres- 

 ponding to the carinse. Surface marked by irregular, sinuous 

 lines of growth. Indications of fine revolving striae are seen 

 on the casts. Maximum diameter of a large specimen, three 

 inches. 



All the known specimens of this line species are in the form 

 of casts in magnesian limestone. 



Found in the Niagara limestone at Monmouth, Iowa. 



Straparollus tricarinatus, n. s. 



PLATE II., FIGS. 2 a, b. 



Shell of medium size, smaller than the preceding, spire de- 



