Development and Mode of Growth of Biplo- 

 graptus, McCoy. 



Br R. RUEDEMANN. 



In the picturesque gorge of the East Canada creek, near Dolge- 

 ville, N. Y., is found, intercalated in typical black bituminous 

 Utica slate, a very thin brown argillaceous layer which has 

 proved to be covered so densely with the compound fronds 

 of Dijplograjptus Bitedemanni, Gurley,* that those which I have 

 obtained by taking off the overlying shale are counted by hun- 

 dreds. Some very complete fronds of the same species were 

 found in a piece of limestone on the talus of the cliff, appar- 

 ently derived from one of the limestone beds which are associ- 

 ated with the shale. The colonies from this rock are especially 

 instructive, because they are not much compressed and show the 

 formation of the frond in relief. 



Since this discovery I have given special attention to the search 

 for complete fronds of Graptolites, for such have been described by 

 Prof. James Hall from the Quebec epoch {Monoprionidm). I was 

 rewarded by finding another, unfortunately only temporary, 

 exposure in the Utica slate at DolgevilleJ which was very rich 

 in compound fronds of Dijplograptus pristis, Hall. The fossils 

 of both localities are in such good state of preservation that they 

 reveal many facts regarding the organization and development 

 of Graptolites. 



Until the classical memoir of Prof. Hall on the Graptolites of the 

 Quebec group, only simple linear stipes, or stipes which differed 

 little from the linear ones, were known. Hall made us acquainted 

 with numerous species, the fronds of which are connected in the 

 center by a common stem, the "funiole," from which they 

 branch by bifurcation. The simplest forms with the funicle have 

 four stipes. Continued dichotomy of the four branches pro- 



* This form, which the author, in a preliminary note (cf . The American Journal of Science, 1895, 

 vol. XLIX, p. 453) had identifled as Diplograptus pristiniformis. Hall, has been since described as a 

 new species by R. R. Gurley (cf. The Journal of Geology, 1896, vol. IV,). 



