PLATE XYIII. 
Plettrotomaria Lucina. 
Page t>7. 
Figs. 1, 2. Lateral and vertical views of a small rotund specimen, which is mostly an internal cast, but shows 
the form of the volutions. From the Upper Helderberg limestone, Falls of the Ohio. 
Figs. 3, 4. Lateral and summit views of the original specimen figured in the Fourth District Report, showing 
the .general features of the shell, but not the surface-markings. From the Upper Helderberg 
limestone, Clarence Hollow, N. Y. 
Figs 5, 6. Two views of a large internal cast. From the Upper Helderberg limestone, near Columbus, Ohio. 
Fig. 7. A very large internal cast, probably of this species. From near Batavia, 1ST. Y. 
Figs. 8, 9. Summit and lateral views of a large, well-formed specimen, retaining the surface-marking more 
perfectly than usual in the limestone, and showing the spiral band with its characteristic features. 
The spiral band is not seen upon the second volution, although the surface texture is partially 
preserved. From the Upper Helderberg limestone, Clarence Hollow, N. Y. 
Figs. 10, 11. The opposite sides of a large compressed specimen, with surface-markings much stronger 
than the preceding. From the Hamilton group, near Skaneateles Lake, N. Y. 
Loxonema laxa. 
Page 49. 
Fig. 12. An internal cast. From the hard layers of the Chemung group, near Nichols, Tioga county, N. Y. 
