SOME NEW MIDDLE CAMBRIAN FOSSILS FROM BRITISH 



COLUMBIA 



By Rudolf Ruedemann 



New York State Museum, Albany, N. Y. 



The Middle Cambrian faunas of British Columbia, particularly 

 the marvelous assemblage of organisms from the Burgess Pass, dis- 

 covered by Dr. Charles D. Walcott in 1910 and studied by him 

 throughout the remainder of his life, continue to afford most inter- 

 esting subjects for research. A small group of these fossils from 

 the Burgess shale and the Stephen formation was sent me some time 

 ago by the authorities of the United States National Museum for 

 further study. In their general appearance they suggest graptolites, 

 and as such had been laid aside for future study by Doctor Walcott. 

 Upon close study, however, they have proved to be an unusually 

 interesting and at the same time difficult assemblage of fossils, none 

 of which belong to true graptolites. It is with the full realization 

 of the tentative nature of the determinations that the following 

 results of my studies are published. 



ALGAE 

 DICTYOPHYCUS GRACILIS, new genus and species 



Plates 1, 2 



This form consists of a reticulate network of delicate fibers, which, 

 looked at with the naked eye, strongly suggests Dictyonema. With 

 the aid of a microscope, however, the organism is seen to have no 

 trace of thecae or of any other graptolitic structure except a number 

 of irregularly distributed circular pores, the occurrence of which maj^ 

 or may not be accidental. The fibers themselves lack the strong con- 

 sistence and glossy appearance that the chitinous tests of graptolites, 

 as a rule, possess and suggest rather the softer tissue of plant life. 



A study of the changes that take place in recent algae when decay 

 sets in reveals the fact that in a form such as Chlorodictyon foUosum, 

 J. G. Agardh, one of the Caulerpaceae, the originally flat, broad, leaf- 

 like expansions of the thallus become so perforated by the decay 



No. 2893.— Proceedings U. S. National Museum, Vol. 79. Art. 27. 



66548—31 1 1 



