404 REPORT ON THE STATE CABINET. 



GENUS LITUITES, Breyn. 



LiTUITES MARSHII, N. S. 

 PLATE XVI, FIGS. 6, 7. 



Shell of medium size, consisting of three or more closely enrolled volu- 

 tions, which increase in size very gradually from the apex : section 

 circular or subcircular; slightly flattened on the dorsum, and marked 

 on the sides by sharp, strong, oblique annulations with regularly 

 concave spaces between. These ridges, rising on the ventral 

 margin, are directed obliquely backward as they cross the sides of 

 the volutions, reaching the centre of the dorsum at a point opposite 

 the origin of the second preceding one, having their greatest eleva- 

 tion on the sides of the shell, and making a somewhat abrupt retral 

 curve, become nearly obsolete on the dorsum. Septa moderately 

 distant, deeply and uniformly concave ; the chambers regularly 

 increasing in depth with the diameter of the shell. The space of 

 three chambers, measured on the side of the shell, are equal to the 

 dorso-ventral diameter of the volution. The dorsal margins of 

 the septa are directed forward, giving a broad retral curvature on 

 the sides of the volution. Siphuncle small, subcentral. Sui'face 

 of shell and form of aperture unknown. 



This beautiful species is readily distinguished by its slender volutions, 

 and the strong oblique ridges, which in the outer part of the shell are a 

 little more distant than the septa, while on the inner volutions they are 

 nearer to each other, the increase in the distance of the annulations 

 being a little more rapid than that of the septa. Owing to the retral 

 curving of the annulations, and the advancing curvature of the septa, 

 the ridges are cut by the latter near the dorso-lateral angle of the volu- 

 tion, throughout the greater part of the extent of the shell. The 

 specimen preserves a little more than two volutions, and we have no 

 portion of the chamber of habitation. Inferring from the prevailing 

 characters of similar forms of this genus, there has probably been nearly 

 or quite another volution at the apex, which is not preserved. 



Formation and Locality. — In limestone of the Niagara group, at Kan- 

 kakee, Illinois. 



