GRAPTOLITES OF NEW YORK, PART 1 537 



Dictyonema, according to Wimau, a generation preparative to a branching- 

 produces a theca and two budding individuals instead of a theca, a budding 

 individual and a gonaugium. Each of the budding individuals then 

 produces the three kinds of individuals ; the resulting two groups of 

 individuals forming with one or more of the old thecae, the new branches, 

 which are thus of perfectly dichotomous origin. In the forms referred by the 

 same author to Dendrograptus the process is essentiall}- the same, In 

 Inocaulis one has to differentiate between branches and branchlets or 

 twigs. Each of the latter consists of four individuals, t\vo thecae and two 

 gonaugia, which originate in the branches and open on the twigs. In Cal- 

 lograptus the mode of the formation of branches is not yet known. 



In the axonolipous Graptoloidea branching is accomplished by two 

 successive thecae, which turn to different sides and thus become the mother 

 thecae of new branches. In the early axonophorous Graptoloidea, described 

 in this publication, no branching takes place within the I'habdosomes or 

 persons of the second order. 



The arrangement of the branches varies greatly in the Deudroidea ; the 

 branches are distributed irregularly in treelike fashion in Dendrograptus, 

 arranged into a funnel or bell-shaped rhabdosome in Dictyonema, into a similar 

 or probably flabellate form in Callograptus, while in Ptilograptus the 

 irregularly arranged branches are plumose, the branchlets rising alternately 

 on opposite sides of the branches. 



In the axonolipous Graptoloidea the earliest genera, Clonograptus and 

 Bryograptus, possess an irregular arrangement of the branches. From these 

 two develop, by a progressive reduction in the number of branches, forms 

 with a regular disposition of the branches, namely the genera Loganograptus, 

 Dichograptus, Tetragraptus, Didymograptus and Phyllograptus, forming one 

 group, the genera Sigmagraptus, Coenograptus, Pterograptus and Pleuro- 

 graptus another, and the genera Temnograptus, Schizograptus, Ctenograptus, 

 Holograptus, Rouvilligraptus and Trochograptus, a third. 



In the first group only dichotomous branching is observed, in the others 

 the dichotomous and monopodial modes of branching form various combina- 



