2l8 NEW YORK STATE MUSEUM 



least are probably composite in character and that in these thicker branches 

 the pores are placed directly under the points of bifurcation, while in 

 terminal undivided branches they appear in continuous series. The dis- 

 tances between them are, however, as a comparison of text figure 115 and 

 plate 12, figure 1 will show, in both exactly equal, a fact which suggests 

 that there is no essential difference in structure between the proximal and 

 distal parts of the rhabdosome. 



Walcott has already recognized the similarity of his species to M . 

 (Psilophyton Lesq.) gracillimus (Lesq.) by pointing out their 

 differences. M. tenuiramosus is said to have "smaller cellules and 

 less robust stipe and branches," and Ulrich, the discoverer of the Cincinnati 

 species, James, Harper and Bassler have all listed the two species sepa- 

 rately, all of them referring Lesquereux's Psilophyton g r a c i 1 1 i m u m 

 to the graptolites, viz, to Dendrograptus. 



Mastigograptus simplex (Walcott) 



Plate 9, figure i ; plate 12, figures 3-5 



Dendrograptus simplex Walcott. Utica Slate and Related Formations. 1879. 



p. 20 



Dendrograptus simplex Walcott. Alb. Inst. Trans. 1883. 10:20; pi. 1, fig. 5, 



5 a , 5V6 



Dendrograptus simplex Walcott. Geol. Soc. Am. Bui. 1890. 1:347 



Dendrograptus simplex ? Ami. Can. Rec. Sci. 1892. v. 5 



Dendrograptus simplex Gurley. Jour. Geol. 1896. 4:300 



Description. Rhabdosome of large size (large fragmentary rhabdo- 

 somes measure 20 cm and more in length), of Militant appearance, the 

 extremely slender, uniformly thick (about .1 mm— .45 mm) and very long 

 branches being very flexuous in form and out of proportion thin to their 

 length, suggesting the floating branches of aquatic plants. 



The branching is monopodial or lateral, taking place at varying angles 

 (6o°-90°), alternating in distances of about 3 mm, but mostly appearing 

 irregular and infrequent, probably through the loss of numerous secondary 

 branches. 



