PLATE ex. 



Nautilus (Discitbs) inopinatus. 



Pago 428. 

 Fig'. 1. A lateral view of the specimen, showing the wiiie umbilicus, the form of the volutions, and the rows 

 of nodes upon the umbilical and peripheral margins. The surface is obscured by adhering 

 Stromatopoha. 

 Fijf. 2. The ventral side of the specimen, which preserves a part of the shell, obscurely showinjf the surface- 

 markings. Kear Sandusky, Ohio. 

 « 



GONIATITES PLEBEIF0RMI8. 



Pajre Hi. 



See Plate l(i. 



Fig. 8. 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-peraha cast in a natural 

 mould of the fossil. The impressions of the nodes have been only partially pi-eserved. 



Fig. 6. The outer volution of a lai'ge 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 chamlier of 

 habitation, terminated with the last septum of the chambei-ed portion of the shell. The inner 

 volutions have all disappeared, and the space is occupied by calcareous matter filled with 

 Styliola and Tkntacdlitks. 



Fig. 8. A section of a specimen, cut in the direction of the spire, preserving the grand chamber and a small 

 jiart 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 jii-eserved, 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 jwrtion of the figure. The septate portions of the volutions are rarely preserved. 

 Cherry Valley, N. Y. 



