INVERTEBRATE A-NIMALS IN PALEOZOIC ROCKS. 



613 



§ VII. Eranching Tracks. (Fig. 9, page 605.) 



It is very puzzling to the Ichnologist to find so many impressions 

 which he would regard as of animal origin branching in a manner 

 to simulate plants. The distinction, however, between branching 

 plants and branching tracks is usually sufficiently obvious to an ex- 

 perienced eye. The latter are generally of the nature of more or less 

 cylindrical bodies, divergingor radiating from a commoncentre ; while 

 the former display either alternate ramification or bifurcation. As 

 examples I may refer to Photograph No. xiii. (not figured) oi Bu- 

 thotre'phis gracilis, and B. Orantii, figs. 16 and 17, true Eucoids, in 



Pig. 16.- 



-ButhotrepJiis Grantii. 



Silurian of Canada. 



A true Fucoid, from the 



comparison with fig. 9 (above referred to), of radiating Annelid 

 marks, or Photograph No. xv. (not figured), which represents a 

 Licrophycus, probably a burrow with diverging tracks. Simple 

 and branching trails of these kinds cover large surfaces of the Cal- 



