GASTEROPODA. 91 



MURCHISONIA LEDA. 



PLATE XXI, FIG. I. 



Murchisonia Leda, Hall. Fourteenth Rep. N. Y. State Cab. Nat. Hist., p. 103, 1861. 



" " " Fifteenth Rep. N. Y. State Cab. Nat. Hist., p. 162, pi. 4, fig. 10. 1862. 



Shell elongate, terete or subfusiform. Volutions rounded (number unknown), 

 somewbat rapidly expanding. Aperture subelliptical. 



Surface marked by strong, elevated tbread-like striae, which are nearly vertical 

 on the upper part of the volution, but turn gently backward towards the 

 centre where they reach the revolving band, below which they are turned 

 a little forward in a direct line to the suture. Peripheral band flat, 

 limited above and below by a distinct carina, its upper margin being 

 scarcely above the centre of the volution. 



This species has the general aspect of a Loxonema, and in casts of the 

 interior it is not possible to distinguish its generic relations ; the striae are of 

 the same character as in the prevailing forms of that genus ; it differs little in 

 form from L. pexata, the volutions being a little more rounded, and the spire 

 more rapidly attenuate. The volutions are also more rounded than in M. Maia. 

 The simple suture and flattened peripheral band are distinguishing features. 



Formation and locality. In limestone of the Upper Helderberg group, at 

 Cambridge, Ohio. 



Murchisonia Maia. 



PLATE XXI, FIGS. 5-9. 



Murchisonia Maia, Hall. Fourteenth Rep. N. Y State Cab. Nat. Hist,, p. 103. 1861. 



« •• " Fifteenth Rep. N. Y. State Cab. Nat. Hist., p. 162, pi. 4, fig. 11. 1862. 



Shell elongate, turretiform; spire somewhat rapidly ascending. Volutions 

 eight or more, gradually expanding from the apex, rounded above and 

 below, very obtusely subangular on the periphery — the last volution a 

 little more ventricose than the preceding. Aperture broadly oval, a little 

 longer than wide, with the columellar lip extended below. 



