STUDY OF THE ORAPTOLITES. 



207 



In tlie next stage we have four simple stipes diverging from an initial 

 point, and all evidently entire, as shown in the development of the 

 cellules in GraphUthus {Didijmograptus) hryonoides (fig. 3). 



In some species of this mode of growth, the bases of the stipes are 

 united in a more or less expanded disc or cup of the same substance as 



Fig. 6. 



Fig. 6a. 



Fig. 7. 



the body of the graptolite. The form of this disc is shown in fig. 4 of 

 Graptolitlms {Loganograptus) lieadi. 



In a further development in the same direction, we have fronds with 

 eight simple stipes, which may or may not be united in a central disc, 

 as in G. {Loganograptus) octohrachiatus (fig. 5). 



