638 NEW YORK STATE MUSEUM 



BRYOGRAPTUS LapWOPtll. 1880 



The genus Bryograptus was erected by Lapworth [1880, p.l64] for 

 forms witL. the following characters : " polypary bilaterally subsymmetrical, 

 consisting of two compound monoprionidian branches diverging at a small 

 angle from a well marked sicula, and originating similar compound (or 

 single ?) secondary branches at close but irregular intervals from one mar- 

 gin only. Hydro thecae minute, of the type of those of Dichograptus 

 Salter." 



This genus is remarkable for two facts, the irregularity of its branch- 

 ing and its early appearance. These facts and the great similarity of the 

 species of Bryograptus to species of later genera with more regular branching 

 indicate at once that the genus is a synthetic one, and stands in ancestral 

 relation to various simple, more regularly branched graptolites. We have 

 discussed these relations in the chapter on the classification and phylogeny of 

 the graptolites [p.554], to which we refer the reader. 



Elles and Wood have divided the British forms into two series, a depen- 

 dent and a deflexed series. Each of these is represented at the Deep kill by 

 one species. 



The gemmation of the first thecae could be observed in B . 1 a p • 

 wort hi and has been described under that caption. It is like that of 

 other Dichograptidae and specially like that of the Didymograptidae. The 

 dichotomous branching also takes place in a manner identical with that 

 described by the writer of Goniograptus thureaui and other 

 Dichograptidae [1902, p.583], viz by the successive budding of two thecae, 

 the second of which buds from the first, and both of which assume diverging 

 directions. 



The genus Bryograptus can be said to hover around the boundary 

 line between Cambric and Siluric, for its species belong all either to the 

 uppermost Cambric or lowest Lower Siluric, or to the transitional beds 

 between the two, as B. kjerulfi, the genotype of this group, in the 

 region of Christiania. In America thus far only some forms from the 



