PLATE Clir. 



Gyroceras Cyclops. 



I'age S87. 

 See Plates lUI, 102, 104. 

 Fig'. 1. A fragment, showing the transverse section of the tube and one of the foliate expansions of the test, 

 with its piii-face-niarkings and the strong plit^alions of the margin, which are more subdued at 

 the base and along the walls of the tube. Ujip«T Helderberg limestone. Qiliunbiis, Ohio. 

 Fig. 2 id. Lntei-al view, showing the surface-markings on the tube ami the inclination and extension of the 

 tiausverse expansions. 



Gyroceras Eryx. 



Pago 3-«. 

 See Plate 5S. 

 Rg. 8. Lateral view of a large individual, showing the size and curvatui-e of the shell. Some of the septa 

 are preserved, and ehow the regular depth of the air-chambere and the straight septal sutures 

 at inpht angles to the spiral axis of tlie tube. Magnesian limestones of the Hamilton group. 

 Neai- Milwaukee, Wit. 



Gyroceras, sp. indet. 



Fig. 4. A fi'ngment found in the same association with ff. Eryx, but of undetermined specific relatione. 

 The tigure is a ventral view, and shows traces of the siphuncle exposed in the process of 

 weathering. Magnesian limestones of the Hamilton group. Near MUxoaukee, Wis. 



