EXPLANATIONS OF PLATE XX. 



DiCTYONEMA IRREGULARIS, page 136. 



Pig. 1. A fragment from near the base of a frond. 

 " 2. A fragment from the outer portion of the frond. 



DiCTYONEMA EOBUSTA, page 137. 



Figs. 3, 4. Fragments of two different fronds. In some parts of the specimen fig. 3, and 

 in all of fig. 4, the branches are extremely flattened and attenuate. 



DiCTYONEMA QCADRANGULARIS, page 138. 



Fig. 5. A fragment of a frond, of the natural size. 



DiCTYONEMA MuRRAYi, page 138. 

 Figs. 6, 7. Fragments of two fronds ; the figures of the natural size. 



