PLATE 2 7. 



Paso. 



Fig. 1. Nautilus Dekayi 496 



1, a. A peripheral and aperture view of a small specimen, consisting of the inner septate volu- 

 tions. 

 1, 6. A side view of same. 



1, c. A peripheral view of another specimen, showing the sinuosity of the lip. 

 1, d. A side view of a younger specimen. 



1, e. Surface-markings of last, magnified. 



Fig. 2. Nautilus Dekayi, var. Montanaensis 4'J8 



2, a. A side view of a large specimen of septate part, being maiuly an internal cast (type of 



the variety). 

 2,6. A peripheral and aperture view of same. 

 2, c. A peripheral and aperture view of a young shell. 

 2,tf. A side view of same. 

 2, c. Surface-markings of same, magnified. 

 2,/. A side view of a larger specimen. 



