STUDY OF THE GRAPTOLITES. 



Fig. 6. 



175 



Graptolithus logani. 

 The stipes of this species do not bifurcate beyond the disc, and there 

 are no cellules below the last bifurcation. The number of stipes in differ- 

 ent individuals varies from sixteen to twenty-five, so that this character 

 cannot be made of specific importance. In another similar species without 

 a central disc, G. multifasciatus from the Hudson-river formation, we have 

 above forty stipes, which do not bifurcate, so far as known, beyond the 

 commencement of the cellules. 



