GEOLOGY OF THE FOURTH DISTRICT. 



ORGANIC REMAINS OF THE HAMILTON GROUP. 



No. 47. — No. 85, page 207. 

 Fig. 1 . Dclthyris granulifera. 

 Fig. 1 a. End view of the same, showing the spiral coil within the shell. Pavilion, Genesee 



county. 

 Fig. 1 h. A specimen with a more extended hinge line, Moscow. 

 Figs. 1 c and 1 d. A younger shell of the same species. Pavilion. 

 Figs. 2 and 2 a. Delthyris congesta, H. Seneca lake shore. 

 Fig. 3. Dclthyris mucronata, H. View of the hinge. 

 Fig. 3 a. Area of lower valve. 

 Fig. 3 b. Lower valve. Moscow. 



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