EXPLANATION OF PLATES. 



PLATE I. 



Figure 3. A group of orthic tetrakaidecahedra. 



Figures 4, 5, and 6. Three views of a model of cell e in Figure 2, having fif- 

 teen surfaces. X 275 diam. 

 Figure 7. Model of cell a in Figure 2, having fifteen surfaces. X 333 diam. 



PLATE II. 



Figures 8 and 9. Orthic tetrakaidecahedra utilized to show the restoration 



of the original form following transverse division. 

 Figure 10. Model of a pair of cells, evidently resulting from a transverse 

 division, lettered to correspond with Figures 8 and 9. The 

 upper cell has 16 contacts, the lower, 13, being cells b and c of 

 Figure 2, inverted. X 266 diam. 

 Figures 11 and 12. Orthic tetrakaidecahedra divided vertically through the 

 angles, and through the sides, respectively, of their top and 

 basal surfaces. 

 The right half of Figure 12, for comparison with Figure 14. 

 Model of a cell with 11 surfaces, produced from a tetrakaideca- 



hedron by vortical division. X 333 diam. 

 Model of a cell with 18 surfaces, which through transverse divi- 

 sion, accompanied by that of certain adjoining cells, would 

 produce conditions similar to those in Figure 16. X 250 diam. 

 Model of a pair of cells, evidently resulting from a transverse 

 division, showing atypical features explained in the text. 

 X 225 diam. 

 Model of a pair of cells resulting from an unequal transverse 



division. X 333 diam. 

 Portion of an orthic tetrakaidecahedron for comparison with 

 Figure 19. 

 Figure 19. Model of a small flattened cell having six surfaces. X 270 diam. 



Figure 13. 

 Figure 14. 



Figure 15. 



Figure 16. 



Figure 17. 

 Figure 18. 



PLATE III. 



Figure 20. A group of orthic tetrakaidecahedra for comparison with Figure 



21. 

 Figure 21. A group of seven cells (the central cell being d of Figure 2) 



showing 18 surfaces which correspond in position anil the 



number of their sides with those bearing numerals in Figure 20. 



X 260 diam. 



