EXPLANATIONS OF PLATE IL 

 Climacograptus typicalis. 



Figures 1-8 are enlarged to six diameters. The specimens have the common canal filled 

 with mineral matter so that they are fully distended, except fig. 8 which is partially 

 fiattened from compression. 



Fig. 1. A lateral view of the concave side, with the surface entire, showing the form of 

 the cell-aperture.s. 



" 2. A profile view of the same, showing the entire form of the cell-apertures. 



" 3. Lateral view of a fragment where the surface is exfoliated, showing the cell- 

 partitions extending downwards towards the centre. 



" 4. A longitudinal section made a little below the exterior surface, showing the cell- 

 partitions extending further towards the interior than in fig. 3. 



" 5. A longitudinal section through the centre, showing the cell-partitions reaching 

 to the central axis. 



'' 6. A transverse section, showing the cell-partitions just within the aperture, and 

 the minute central axis. 



" 7. A transverse section made a little lower than in fig. 6, showing the cell-partitions 

 extending across the stipe on one side, arid on the other side showing the 

 narrow triangular point near the centre. 



" 8. A section made diagonally across a crushed stipe, showing the folding (from 

 pressure) of two cell-divisions on each side of the centre. 



*' 9. An ideal longitudinal section, showing the form and direction of the cell-parti- 

 tions and the central axis (enlarged to twelve diameters). 



Graptolithus (Diplograptus) putillus. 



Enlarged to twelve diameters. * 



Fig. 10. A fragment of a stipe, showing the two ranges of cellules, their form, mode of 

 growth, and the infolding of the exterior test along the line of the central 

 axis. 



" 11. A lateral view of the same fragment, showing the cell-apertures, the flat- 

 tening of the exterior of the base of the next cellules in advance, and the 

 greater breadth of the cellules at the bases. 



" 12. A longitudinal section through the centre of the stipe, showing the double 

 cell-partitions and the double central axis. 



" 12 a. A transverse section cutting one cellule near the aperture and the other near 

 the base. 



Climacograptus bicornis. 



(Graptolithus bicornis, Palaeontology of New-York, Vol. i, page 268, and Geology of Canadai 



page 200.) 



Fig. 13. The lower part of a stipe enlarged to two diameters, showing the bifurcating 

 process and a central node or radicle. 



" 14. An enlargement, to six diameters, of a fragment which preserves in a very per- 

 fect manner the borders of the cellules, and shows an undulating central 

 axis as well as the median ridge. 



" 15. The base of a specimen showing three spine-like processes (two diameters). 



" IG. The lower extremity of a specimen showing a partially developed corneous 

 disc (two diameters). 



'' 17. The lower extremity of another specimen, showing a more complete disc or 

 bulb at the base (two diameters). 



