426 NEW YORK STATE MUSEUM 



PLATE 16 



Genus phragmostoma Hall 



Page 322 



Phragmostoma natator Hall 



Page 325 



i, 2, 4, 5 Specimens from the Cashaqua shales showing the usual form 

 and the concentric surface markings 



Naples subprovince Naples and vicinity 



3 A smaller example 



Naples subprovince 



Genundewa limestone, Canandaigua lake 



Phragmostoma cf. triliratum Hall 



Page 327 



6 An incomplete specimen showing the divergent dorsal ridges 



on the lateral slopes of the shell 



Naples subprovince Hamilton gully, Honeoye lake 



Phragmostoma incisum Clarke 



Page 327 



7 An entire specimen showing the marginal outline and the 



incised revolving lines, xi.5 



8 Front view of a replacement showing the striation. X3 



Naples subprovince Whetstone gully, Honeoye lake 



9, 10 Two views showing the normal contour of the shell but 



incomplete at the marginal outline. X3 



Naples subprovince Naples 



1 1 — 1 5 Views of barite replacements showing the form of the flattened 



and excavated umbonal callus with the reflected lip. 11,13 



and 15, X3 ; 12 and 14, X2. Figure 15 is from the same 



specimen as figure 8. 



Naples subprovince Whetstone gully, Honeoye lake 



16, 17 Two small specimens from the shales 



Naples subprovince Naples 



