PLATE XLI—Continued. 
M OI )IOMORPHA RIG I DA. 
Page -287. 
Figs. 14-16. Left valves in their natural form and proportions. 
Chemung group. Alleghany Co., N. Y. 
Fig. 17. A specimen vertically compressed ; referred with doubt to this species. 
Chemung group. Belmont, N. Y. 
Moihomorpha quadrula. 
Page 289. 
Figs. 18-26. Figures presenting the prevailing varieties of form in this species. 
Chemung group. Alleghany and Cattaraugus counties, N. Y. 
PtychoDICSMA minor. 
27. A right valve of this species. 
Chemung group. 
Page 353. 
Near Elmira, N. Y. 
Modiomorpha hyalea. 
Page 292. 
Fig's. 28-30. Three right valves. In fig'. 30 the radii are too strongly represented. 
Waverly sandstone. Granville, 0. 
