200 DuTVOSI'OiNCilD.K. 



PLATE XXXI. 



ACTINODICTYA, Hall. 



Page 142. 

 (See Ph>te XXX ) 



ACTINODICTYA PLACENTA, Ilall. 



Page 143. 



(See Plate XXX ) 



Figure ] . A very nearly complete froud showing the regularity of much of 



the finer reticulation. 



Chemung group. One-half mile from, Broton hill school house 



near Cohocton, New Yorh. 

 Figure 2. A small frond, with well defined margins indicating completed 



peripheral growth. 



Chemung group. Brown hill colony, near Cohocton, New Yorh. 



CRYPTODICTYA, Hall. 



Pago 144. 

 (See Pl.ite XXXII.) 



Cryptodictya Alleni, Hall. 



Page 144. 

 (See Plate XXX 11 ) 



Figure 3. A portion of a nodose margin of a specimen which shows that 

 these nodes bore tufts of spicules. Such tufts are seen only when 

 the nodes lie at the mai-gins of the surface expansion and the tufts 

 extend along the plane of lamination of the matrix. 



Figure 4. An irregular frond showing on one side the abrupt depression of 

 the nodose surface to the broad, anodose marginal expansion. 



Figure 5. A large specimen in \vliich the nodes are arranged in groups. 

 This frond has been folded along the i-ight margin, the opposite 

 side being of the same extent as that here represented, and having 

 the nodes similarly arranged in clusters. This folding of the frond 

 is, however, probably Avholly due to compression. 

 Chemung group. Lyndon, Cattaraugus county, New Yorh. 



