PLATE XYIII. 



Pleurotomaria Luoina. 



Page 07. 

 Fi^. 1, 2. Lateral and vertical views of a small rotund sjiecimen, which is mostly an internal cast, but shows 



the form of the volutions. From the Upper Helderbergr 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, pi-obably of this species. Prom near Batavia, N. Y. 

 Figs. 8, 9. Summit and latci-al views of a large, well-formed specimen, retaining the sm-face-marking more 



perfectly than usual in the limestone, and showing the spiral band with its characteiistic features. 



The spiral band is not seen upon the second volution, although the surface textui-e is partially 



preserved. From the Upper Helderberg limestone, Clarence Hollow, N. Y. 

 Figs. 10, 11. The opposite sides of a large compressed 8i:>ecimen, 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 layere of the Chemung group, near Nichols, Tioga county, N. Y. 



