PLATE CX. 
Nautilus (Discites) inopinatus. 
Page 426. 
Fig. 1. A lateral view of the specimen, showing the wide umbilicus, the form of the volutions, and the rows 
of nodes upon the umbilical and peripheral margins. The surface is obscured by adhering 
Stromatopora. 
Fig. 2. The ventral side of the specimen, which preserves a part of the shell, obscurely showing the surface- 
markings. Near Sandusky, Ohio. 
Goniatites plebeiformis. 
Page 448. 
See Plate 1G. 
Fig. 3. A young specimen preserving the chamber of habitation only, the inner volutions having been dis¬ 
solved by iron pyrites. 
Fig. 4. A larger specimen, the form and proportions being given from a gutta-percha cast in a natural 
mould of the fossil. The impressions of the nodes have been only partially preserved. 
Fig. 5. The outer volution of a large specimen preserving only the grand chamber; the septate portion 
having been removed by the action of iron pyrites. 
Fig. 6. The ventral side of an interior volution, showing the course of the septa and the angular re-entrant 
lobe. 
Fig. 7. A section of a specimen of the prevailing size and proportions, showing the depth of the chamber of 
habitation, terminated with the last septum of the chambered portion of the shell. The inner 
volutions have all disappeared, and the space is occupied by calcareous matter filled with 
Styliola and Tentaculites. 
Fig. 8. A section of a specimen, cut in the direction of the spire, preserving the grand chamber and a small 
part of one of the chambered volutions. The remaining portion of the cavity is filled with 
limestone containing Styliola. 
Fig. 9. A section of a specimen cut vertically through the spire and the adhering limestone. The section 
of the outer volution is preserved, as shown in the figure, while the inner turns have been 
dismembered and displaced, as shown by the small semi-elliptical sections preserved in the 
central portion of the figure. The septate portions of the volutions are rarely preserved. 
Cherry Valley, N. Y. 
