EXPLANATIONS OF PLATE IIL 

 Graptolithus quadrimucronatus. 



Fig. 1. Enlargement of part of a stipe compressed in a slightly oblique direction, still 

 showing the cellules on the two sides. 



'• 2. Enlargement of a stipe compressed more obliquely, so as nearly to obscure the 

 cellules on one side. 



" 3. Enlargement of a specimen compressed vertically to the celluliferous sides of 

 the stipe. 



" 4. A diagram representing a theoretical longitudinal section. 



^' 5. A transverse section of a stipe, with the mucronate extensions of the cell- 

 margins. 



Graptolithus amplexicaule. 



Fig. 6. Enlarged view of the back of a portion of a stipe, showing the form and direc- 

 tion of the cells. 

 " 7. Enlargement of the inner face, showing the curvature and overlapping of the 

 cells and the quadrangular apertures. 



Graptolithus nitidus. 



Fig. 8. A large specimen showing the radicle and two stipes, and the pustules at the 

 base of the cellules. The extremities are not quite entire. 

 *' 9. A well preserved small individual, enlarged to three diameters. 



Graptolithus flaccidus. 



Fig. 10. An enlargement, to three diameters, of the radicle and stipe bases with the 

 cellules. 

 " 11. A further enlargement of a portion, to show the form of the cellules and the 

 pustuliform appearance at the base of the divisions between them. 



Graptolithus extensus. 



Fig. 12. An enlargement of a fragment of a stipe, where the cellules are distended by 

 iron pyrites. 



Graptolithus bifidus. 



Fig. 13. An individual of ordinary size. 

 *' 14. An enlargement of one of the stipes of another individual, showing the form 

 of serratures, and minute pustules at the base of the cell divisions. 



Graptolithus fruticosus. 



Fig. 15. An enlargement of one stipe, with the bases of the other three, showing the 

 form of cellules and mode of bifurcation in this species. 



Graptolithus bryonoides. 



Fig. IG. An enlargement of the base of a specimen, showing the initial point, the cell 

 denticles on one of the stipes, and a proportionally longer funicle than usual. 

 " 17. An enlargement of a young individual showing tlie radicle, funicle, and origin 

 of the four stipes, with a few of the earlier cellules. 



