394 REPORT ON THE STATE CABINET. 



Pleurotomaria axion, n. s. 



PLATE XV, FIG. 17. 



Shell subcorneal, volutions about four, the apicial one minute, the first 

 three volutions small, rounded and gradually expanding, while the 

 last one becomes extremely ventricose and evenly rounded ; suture 

 line deeply impressed and more than half of the preceding volution 

 exposed above it. The aperture has been subcircular and very large. 

 Surface marked by strong revolving striae, which are crossed by 

 concentric stri^ of less strength, giving a cancellated structure. 

 The middle of the volution is marked by a rather wide and little 

 elevated band, upon which the striae have a slight retral curve. 



The surface characters are very similar to those of P. Iuci7ia of the 

 Lower Helderberg and Hamilton groups of New York ; but the shell is 

 more elevated and attenuate towards the apex, and the suture is more 

 deeply marked. Its form is intermediate between the species just cited 

 and P. lineata.* 



The species described is from a gutta-percha cast and an impression 

 in limestone. 



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

 at Bridgeport, Illinois. 



GENUS TROCHONEMA, Salter. 

 Trochonema (Eunema) fatua, n. s. 



PLATE XV, FIGS. 7, 8. 



Spire elevated ; shell turritiform, consisting of about four or five volu- 

 tions, which gradually increase to the last one which is moderately 

 ventricose ; volutions biangular, leaving a flattened space upon the 

 back about equal to the flattened space between the upper angle and 

 the suture line ; lower side of the last volution rounded ; aperture 

 ovate-elongate. 



The specimens are casts of the interior, and in this condition are 

 readily distinguished from any other species of similar form in these 

 rocks. 



* See Fifteenth Report on the State Cabinet of Nat. Hist., p. 165, Plate v. 



