PLATE XLYIII. 



GtROCERAS 8PIN0SUM. 



I'age 38-2. 



See Plates 47, 49, 98, 99. 



Fig. 1. A chaml>ered fragment, showing the inner volution of the shell and the bases of one of the lateral 



rowB of spines. The air-chambei-s near the apex ai-e numerous, becoming gradually deeper 



toward the aperture. Schoharie grit. Schoharie, N. Y. 

 Fig. 2. A small, coinpi-essed fragment, showing somewhat deep«r air-chambers than in the preceding 



specimen. Schoharie, N. T. 

 Fig. 3. Lateral view of a fragment, preserving its natural, uncompressed form, showing portions of the 



test and the bases of sevei-al of the lateral and ventral spineS; Schoharie, N. Y. 

 Fig. 4. Lateral view of a portion of the outer volution, preserving the chamber of habitation, with akout 



twenty air-chambei-s. The bases of two lateral rows of spines are obscurely shown iu the 



BI>ecimen, as represented in the figure. Schoharie, N. Y. 

 Fig. 5. Ventral view of a small, well-preserved imiividual, nhowing the enlargement of the tube, the sinus 



in the strije, and the two rows of spines, with the revolving ridges ornamenting the ventral side 



of the tube. A lateral view of this specimen is given on plate 93. Schoharie, N. Y. 



