GASTEROPODA. 87 



Pleurotomaria Itys, var. tenuispira. 



PLATE XXX, FIG. 25. 



Shell turbinate ; spire elevated, suberect, higher than wide. Volutions seven 

 or more, minute above and rapidly expanding below, the last one very 

 ventricose ; the exposed portions regularly rounded. 



Surface marked by somewhat distant, strong, revolving carinate strife, which 

 are crossed by strong concentric striae, producing a nodulose or crenulate 

 character. The revolving striae are regular and equidistant above and 

 below the peripheral band, which is simple, comparatively wide, and 

 marked only by the retrally curving concentric striae. 



The specimen is small and apparently a young form, possessing all the 

 essential characteristics of P. Itys in its surface markings, except that the 

 revolving striae are stronger, and the crenulations coarser. It has a larger 

 number of volutions than any other specimen observed, and the rotundity of 

 the last two volutions is greater than in any of the smaller individuals of that 

 species in the collections. 



Formation and locality. In the shales of the Hamilton group, at Hamburgh, 

 shore of Lake Erie. 



Pleurotomaria capillaria, var. 



PLATE XXX, FIGS. 20, 21. 



Spire small above, with the last volution greatly expanding. The upper side 

 of the volutions marked by the characteristic revolving and concentric 

 stris of the species — the former being few and of unequal strength. On 

 the lower side there are two, three or four of the revolving cariniform 

 i-triee just below the peripheral band; the remaining portion of the 

 lower side of the volution is marked only by the concentric stria? which 

 are sometimes obsolete. 



All the specimens of this form which have been observed are vertically 

 compressed, and the last volution has a great lateral expansion. The only 



