428 NEW YORK STATE MUSEUM 



PLATE 17 



Genus phragmostoma Hall 



[See pi. 16] 

 Page 322 



Phragmostoma chautauquae sp. nov. 



Page 328 



i Side view of the innermost volutions showing the revolving 

 confluent lines. X5 



2 Dorsal view of an older shell in which the seam is developed. 



The revolving lines have disappeared, their place being 



taken by fine concentric lines. X3 



Chautauqua subprovince Smith's Mills 



3 Apertural view of an adult specimen, somewhat incomplete 



but showing the explanate stoma. X2 



Chautauqua subprovince Forestville 



4 Portion of the ultimate whorl. X2 



5 Part of a young shell with coexistent revolving and concen- 



tric lines. X5 



6 Dorsal view of a very young shell in which the peripheral seam 



is only suggested and the revolving lines are seen to be 

 confluent and interrupted, xio 

 7, 8 Two nearly adult shells with concentric ornaments only. The 

 latter shows the premature closing of the peripheral 

 seam, xt, 

 9 An enlargement of a young shell with confluent revolving 

 striae, xio 



Chautauqua subprovince Smith's Mills 



10, 11 Two mature but compressed individuals. X2 



Chautauqua subprovince Forestville 



