PLATE XIII. 
Glyptodesma erectum. 
Page 153. 
See Plates 11, 12, 25, 86 and 87. 
Fig. 1. The right valve of an individual which preserves both valves. This valve retains its normal 
form and shows the muscular scar and pallial line,' while the left valve is distorted by 
compression. 
Fig. 2. An imperfect left valve, showing- the muscular scar and pallial line. 
Hamilton group. Madison Co., N. Y. 
Fig. 3. The left side of a specimen retaining the greater portion of the shell; on the umbo are some 
pustules which indicate points of attachment for small umbonal muscles. 
Fig. 4. The opposite valve of the preceding specimen, showing the muscular scar and pallial line. 
Hamilton group. Hamilton, Madison Co., N. Y. 
Fig. 12. An internal mould of the upper part of a left valve. 
Fig. 13. The interior as obtained from an impression of the preceding, in gutta-percha, showing the 
cardinal folds. 
Hamilton group. Pratt's falls, Onondaga Co., N. Y. 
Fig-. 14. A view of the right side of a specimen retaining both valves, showing the pallial line, muscu¬ 
lar impression, and the comparative size of the two valves. 
Hamilton group. Madison Co., IV. Y. 
Fig. 15. A profile view of a specimen, showing the relative form of the valves and the depth of the shell. 
Glyptodesma erectum, var. obliquum. 
Page 155. 
See Plate 12. 
Fig. 5. An internal mould of a left valve. 
Fig. 6. A view of the interior as obtained from a gutta-percha impression. 
Fig. 7. An enlargement of the cardinal portion. 
Figs. 8, 9. The left and right sides of a specimen which retains the muscular scars and pallial lines, 
and shows the characters of the hinge in the left valve. 
Fig. 10. An enlargement of the cardinal portion of the preceding specimen, showing- the characters of 
the ligamental area and cardinal folds. 
Hamilton group. Onondaga Co., N. Y. 
Fig. 11. An imperfect left valve. 
Hamilton group. Madison Co., N. Y. 
