PLATE IV. 

 Fig. 1. Portion of a frond of Dictyonema crassum. X 6. 



Fig. 2. Same. The indistinct longitudinal wrinkles which are sometimes seen: 

 in this species, are not represented by the figure. X 6. 



Fig. 3. Monograptus Beecheri, translucent specimen showing tabulation. 



X 60. 

 Figs. 4-8. Monograptus Beecheri. X 60. 

 Figs. 9, 10. Two views of an abnormal specimen of Monograptus Beecheri in 



which for a short distance some of the serrations appear on the unserrated 



side. X 60. 

 Figs. 11-13. Views of M. Beecheri showing character and position of the 



zooidal openings. X 60. 

 Fig. 14. Under surface of the serrations in M. Beecheri, X 60. 

 Fig. 15. End of a specimen of M. Beecheri showing perforated stipe. 



