41 J, REPORT ON THE STATE CABINET. 



strongly constricted at its junction with the septa, and expanded 

 between. Surface of cast (the usual condition in which the specimens 

 are found) obscurely marked by longitudinal ridges in the most 

 perfectly preserved individuals, their distance varying from a six- 

 teenth to an eighth of an inch ; but these are usually so inconspicuous 

 as not to be observed. 



In one specimen, preserving a portion of the outer chamber (fig. 1), 

 the septa become much crowded in the upper part ; but whether this is 

 a constant feature, or only exceptional, cannot be determined. In speci- 

 men figure 2, the septa are oblique to the axis of the shell, caused by 

 the eccentricity of the siphuncle. 



This species is easily distinguished from the others with which it is 

 associated, by its large size, rapidly increasing diameter, circular section 

 and large siphuncle. The exterior surface characters have not been 

 determined. 



Formation and Locality. — In limestones of the Niagara group, at Racine, 

 Wisconsin. 



Orthoceras alienum, n. s. 



PLATE XXIV, FIGS. 5, 6, 7. 



Shell cylindrical, very gradually tapering, a broad constriction of the 

 outer chamber a little below the aperture; septa deeply concave, 

 about four or five in the diameter of the outer one measured ; the 

 length of the outer chamber equal at least to twice the diameter of 

 the shell. Siphuncle central, moderate in size, scarcely constricted 

 at the junction of the septa. Surface of the cast smooth ; exterior 

 surface unknown. 



This species is only known in the form of casts of the interior, and is 

 distinguished from the others described by its very gradual enlargement 

 towards the aperture, below which it is broadly constricted. The shell 

 tapers at the rate of a line in an inch of the length. The siphuncle is 

 a cylindrical tube, which is scarcely constricted at the junction of the 

 septa, and has a diameter of five-sixteenths of an inch where the shell 

 is one inch and three-eighths in diameter. 



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

 Wisconsin. 



