It is known that the branching of the graptolite stipes falls into two types,the dichotomous and the lateral.In the former type the two branches split offsimultaneously and symmetrically with equal magnitude in position;whereas inthe latter type the main stipes and the lateral ones differ considerably.The branching of all the primitive forms of the true graptolites sbelong tothe dichotomous type.Those of laterally Branching stipes began to becomeabundant in the late Lower Ordovician time.It seems probable that the lateral-ly branching forms were derived from the dichotomous type.Goniograptus isa genus representing the transitional form between the two types,as is shownin textfignre 1(p.92).
