STUDY OF THE GRAPTOLITES. 251 



a. Polypaiy simple from the initial point [?J; cells triangular. 



Graptolithus, {Lmnceus) McCoy. 



b. Polypary growing bilateraly and consisting of two simple 

 stipes, or of two stipes which dichotomise at their base. 



DiBTMOQRAPTus, McQoy* [including Teteagraptds, 8alter\. 



c. Polypary compound, growing bilaterally from the initial 

 point, and repeatedly branching in a dichomotous manner. 



DiCHOGEAPTus, Salter. 



d. Polypary compound, growing bilaterally from the initial 

 point, and consisting of four, eight or more simple stipes 

 numerously divided near their base, and below the com- 

 mencement of the cells; furnished with a corneous central 



disc. LOGANOGRAPTUS, Hall. 



e. "Polypary compound, growing in one direction from the 

 primary point;" the subdivisions taking place (by budding) 



from the celluliferous margin. Cyetogeaptus, Oanmthe^'s. 



f. Polypary compound, developed bilaterally from the initial 

 point; cellules on one side of slender branches, which are 

 developed on one oi" two sides of a long slender axis or 

 rachis, the free extremities of which are likewise cellu- 

 liferous. Not branching dichotomously. Ccenogeaptus, Hall, 

 g. " Polypary growing bilaterally, irregularly and repeatedly 

 branching and rebranching, and without a central disc." 



CLADOGiuPTDst, Carruthevs. 

 Slender cylindrical stipes or branches, with tubular cellules arranged in 

 single series. Cellules free throughout their entire length. 



Easteites, Bar7xmde. 



II. 



Polypary with two series of cells, a solid axis, which is slender and filiform 

 or flattened. 



a. Polypary simple, cellules developed in parallel arrangement on 

 two sides of a common solid axis. Stipes narrow elongate. 

 Sub-genus Diprion. Diplogeaptus, McCoy. 



b. Polypary simple, with a double series of cells which are exca- 

 vated in the margins of the stipe. Climacograpius, Hall. 



c. Polypary simple with a double series of cells which are in 

 contact throughout their entire extent ; solid axis excentric ; 

 substance reticulate. Eetiolites, Barrande. 



d. Polypary simple? or compound, with a double series of cells 

 and a bilateral arrangement of the parts in the compound forms. 



Ketiogeaptus, Hall. 



* See supplementary notes. 



t Of Cabeutheks, not Geinitz. 



