PLATE XLI— Continued. 

 MOUIOMORPHA KIGIDA. 



1-iigc -JST. 

 Figs. H-IO. Left vulves in their natural form and jii-oportions. 



Chemung gi-ou|). Alhff/iany C'u., JV. Y. 

 Fig. 17. A specimen vertically compressed ; referi-etl with doubt to this species. 



Chemung g-roup. Belintmt, N. T. 



MoorOMORPHA QUADRULA. 

 Page -JsS. 

 Figs. 18-26. Figures presenting the prevailing varieties of fonn in this species. 



Chemung group. AUeyhany and Vnttaravyiis couvtus, N. Y. 



Ptychodesma minor. 



Page *)3. 

 Fig. 27. A light valve of this species. 



Chennuig group. Near Elmira, N. Y. 



MODIOMORPIIA HVALEA. 

 Page 292. 

 Figs. 28-30. Three i-ight valves. In fig. 30 the radii are too strongly i-epreseuted. 

 Waverly sandstone. Chranmlle, 0. 



