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 stride, 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 
striae 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 
striae just below the peripheral band; the remaining portion of the 
lower side of the volution is marked only by the concentric striae 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 
