PLATE LII. 



Gtkoceras trivolve. 



rage 374. 



See Plate 52 A. • 



Fig. 1. Ventral view of a nearly entire individual, showing- the sinus in the ornaments of the test, and in the 



atinulations of the internal mould. Upper Helderberg limestone. Schoharie, N. Y. 

 Rg. 2. Dorsal view of the preceding. 



Fig. 3. Lateral view of the same, showing the number of volutions and the characters of the internal mould. 

 Fig. 4. A poi-tion of the outer volution of a larger individual, showing moi-e distinctly the annulated character 



of the internal mould, with the rounded longitudinal lidges and strise of the crenulations. 



Schoharie, N. T. 

 Pig. 5. A longitudinal section preserving traces of the septa near the apex ; but for the most part the internal 



characters have been destroyed. 

 Fig. 6. A longitudinal section of a small fragment, showing the depth of the air-chambers and the concavity 



of the septa. Helderberg mountains. 



