VIl] 



OF HEXAGONAL SYMMETRY 



513 



to be more or less in contact with one another (e.g. various Monti- 

 cuHporae) they will be irregular hexagons, while the smaller cells 

 between them will be crushed into all manner of irregular angular 



Fig. 190. Lithostrotion Martini. 

 After Nicholson. 



Fig. 191. Cyathophyllum hexagonum. 

 From Nicholson, after Zittel. 



Fig. 192. Arachnophyllujn pentagonum. 

 After Nicholson. 



m 



m 



Fig. 193. Heliolites. After Woods. 





forms. If on the other hand the large cells are comparatively few 

 and are large and strong-walled compared with their smaller neigh- 

 bours, then the latter alone will be squeezed into hexagons while 

 the larger ones will tend to retain their circular outhne undisturbed 

 (e.g. Heliopora, Heliolites, etc. (Fig. 193)). 



