PLATE XII. 

 Glyptodesma ekectum. 



Page 153. 



See Plates 11, 13, 25. 86 anil 87. 

 Fig. 1. \ left valve. 



Hamilton group. Cazeitovia, N. Y. 

 Fii,'. 2. .\ view (if rig-ht valve showing pallial anil muscular imi>i-e.>«ions. 



Hamilton group. C'azenoina, N. Y. 

 Kip. :i. A left valve jireserving strong, concentric, lamellose sui-face markings. 



Hamilton group. Madison Co., N. Y. 

 Fig. 5. A small light valve jireserving the lateral teeth. 



Hamilton group. Schoharie Co., N. Y. 

 Kig. fi. A very convex left valve. The radiating lines are represented too strongly in the tigui'e. 



Hamilton group. Hamilton, Madison Co., N. Y. 

 Fig. 7. The right side of a cast showing a very distinct muscular scar and pallial line. The appai-ent 

 double impres.sion of the muscular scar is probably due to an irregular growth of this part 

 during its advancement. 

 Fig. 8. A \ cry large and erect left valve, with the cardinal angles much extended. It is of the form of 



Avicula crufiformU, Conrad. 

 Fig. 9. A very large left valve with the test partially exfoliated. 



Hamilton group. Jefferson, Schoharie Co., N. Y. 



Glyptodesma erectum, v:ir. obliquum. . 



I'age 155. 

 See Plate 13. 

 \'\\i. A. A small loft valve nearly complete in form and outline. 

 Hamilton giouji. Cnnandaigua lake, N. Y. 



