PLATE LIX. 



PAGE. 



Figs. 1 to 8 CYRTOCEKAS MINNEAPOLIS, sp. nov 808 



1, 2, 3, 4 Lateral, dorsal and ventral views of a small specimen retaining the shell aud 



preserving the apertural margin. 



5, 6 Ventral and lateral views of another small example with the aperture entire. 

 7, 8 Lateral and ventral views of a larger specimen which is a partial internal cast; 

 showing faint revolving bands interrupting the concentric striae, and the 

 position of the sipho. 

 7a Outline of a septum. From the Trenton shales at Minneapolis. 



Figs. 9 to 11 CYRTOOERAS SCOFIELDI, sp. nov 810 



Dorsal, ventral and lateral views of the typical specimen. From the Trenton 

 horizon at Janesville, Wisconsin. 



Figs. 12 to 15 CYUTOCERAS HOUGHTONI, sp. nov 807 



12 Lateral view of an internal cast of large size. 

 13, 14, 15 Lateral and ventral views of an average specimen. 



14a Outline of a septum, showing the position of tbe sipho and the great lateral 

 compression of the conch. From tbe Trenton limestone, Cannon Falls, Minn. 



Figs. 16, 16a CYRTOCERAS CORNIOULUM Hall SOP 



16 Side view of a specimen, showing the form and curvature. 

 16o Transverse section. Galena shales, Warsaw. 



Figs. 17 to 20 CYRTOCERAS NELEUS Hall 804 



17, 18, 19 Lateral, dorsal and ventral views of a specimen having the body-chamber nearly 

 entire, and showing the nearly gyroceran curvature, the closely set septa and 

 the position of the sipho. 

 17o Outline of a septum at the point of greatest curvature of the conch. From the 



Galena limestone at Wykoff, Minn. 

 20 Lateral view of a less complete specimen. In the Trenton at Beloit, Wisconsin. 



