EXPLANATIONS OF PLATE XXI. 
PTILOGRAPTUS PLUMOSUS, page 140. 
Fig. 1. A fragment which is three times branched. 
(73 
66 
cc 
Fig. 
Fig. 
2 
9. 
€ 
Ge 
A slender simple branch. 
3. An enlargement from the specimen fig. 1. 
4. 
A further enlargement of a portion of the same; some of the branches showing 
markings like cell-apertures. 
PTILOGRAPTUS GEINITZIANUS, page 140. 
A branching fragment showing the celluliferous side. 
. A fragment which is irregularly branched, showing the non-celluliferous side. 
. A single branchlet of the same species. 
. An enlargement from fig. 5, showing the cell-apertures. 
THAMNOGRAPTUS ANNA, page 141. 
A fragment of the species, of the natural size. 
