FROM THE CRETACEOUS FORMATION OF NEBRASKA. 409 



FIG. 7. a, Fusus constrictus, natural size. 

 " 7, Z>, c. Magnified views of the same. 

 " 7, d. Magnified views of surface-markings. 



FIG. 8, a, b. Fusus ? tenuilineatus, two views of a fragment, preserving about two volutions and a half. 



" 8, c. Surface-markings, highly magnified. 



FIG. 9, a, b. Two views of a fragment of the same, showing the aperture. From the collection of B. F. 

 Shumard. 



" 9, c. Surface of same, magnified. 



FIG. 10, a, b. Rostellaria fusiformis, two views of the same individual. 



FIG. 11, a. Dentalium gracilis, fragments, natural size. 

 " 11, b. Transverse section of the larger extremity. 

 " 11, c. Magnified view of surface. 



FIG. 12, a, b. Helix Leidyi, two views of the same individual. From the Eocene Tertiary of the 

 Mauvaises Terres. 



PLATE IV. 



FIG. 1, a. Ammonites complexus, a young individual. 



" 1, b, c. Two views of a fragment of a larger shell. 



" 2, d. Form of the septa, as shown in the young specimen. 



FIG. 1, e. Superior lateral lobe of the adult specimen. 



" I,/. Dorsal lobe of the same individual. 



FIG. 2, a, J, c. Ammonites peracutus, views of different individuals. 



FIG. 3, a. Hamites Mortoni, a fragment. 

 " 3, b. Section of larger extremity. 

 " 3, c. Arrangement of septa in the same specimen. 



FIG. 4. Ancyloceras Nicolletii, a fragment. 



PLATE V. 



FIG. 1, a. Baculites ovatus, showing the form of aperture, surface stria?, and undulations upon the ventral 



half of the shell. 



" 1, b. A fragment, showing septa. 

 " 1, c. Transverse section of the same. 



FIG. 2, a. Baculites compressus, showing the form of the aperture, surface striae, and arrangement of septa 



towards the base of the figure. 

 " 2, b. Transverse section of the same. 

 VOL. V. NEW SERIES. 55 



