Explanations of Plaii<x 283 



ARYSTIDICTYA, gen. nov. 



Page 136. 

 (See Plate XLI.) 



Ajiystidictya eleoans, sji. nov. 



Page 136. 

 (See Plato XLI.) 



Figure 7. The other side of the specimen figured on Plate xli, showing the 

 regular reticulation over the lower part of the cast and the radiating 

 peripheral channels. 

 Lower Chemung group. Cotton Jiill, near Avoca, New York. 



THYSANODICTYA, gen. nov. 



Page 125. 

 (See Platig XIX, XXni, XXIV, XXV, XXVI, XXVII, XXXVIII, XXXIX, XL, XLII, LIII.) 



Thysanodictya scypuina, sp. nov. 



Page 132. 



Figure 8. The typical specimen, showing the undulated basal periloph or 

 fringe of the diaphragm. 

 Chemuug group. Olean, New York. 



