LAURENTIAN AND EARLY PALAEOZOIC. 



29 



CUmactichnites, from the same beds which afford Pro- 

 tichnites. The principal difference between Protichnites 

 and their modern representatives is that the latter haye 

 two lateral furrows 

 produced by the 

 sides of the cara- 

 pace, which are 

 wanting in the for- 

 mer. 



I subsequently 

 applied the same 

 explanation to sev- 

 eral other ancient 

 forms now known 

 under the gener- 

 al name BiloMtes 

 (Figs. 6 and 7).* 



The tubercu- 

 lated impressions 

 known as Phyma- 

 toderma and Caul- 

 erpites may, as Zeil- 

 ler has shown, be 

 made by the bur- 

 rowing of the mole- 

 cricket, and fine examples occurring in the Clinton forma- 

 tion of Canada are probably the work of Crustacea. It is 

 probable, however, that some of the later forms referred 

 to these genera are really Algae related to Caulerpa, or 

 even branches of Conifers of the genus Brachyphyllum. 



Nereites and Planulites are tracks and burrows of 

 worms, with or without marks of setse, and some of the 



* The name Bilobites was originally proposed by De Kay for a bivalve 

 shell (Conocardium). Its application to supposed Alga3 was an error, 

 but this is of the less consequence, as these are not true plants but only 

 animal trails. 



Fia. 7. — Rusophycus (Rusichnites) Grenvillen- 

 sis, an animal burrow of the Siluro-Cam- 

 brian, probably of a crustacean, a, Track 

 connected with it. 



