LAURENTIAN AND EARLY PALEOZOIC. 



29 



ClimacticJiniteSy from the same beds which afford Pro- 

 ticlinites. The principal difference between Protichnites 

 and their modern representatives is that the latter have 

 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 Bilobites 

 (Figs. 6 and 7).* 



The tubercu- 

 lated impressions 

 known as Phyma- 

 toderma and Caul- 



erpites may, as Zeil- Yiq. n,—Rmnphym% {Rusichmtes) Ormvillen- 



ler has shown, be **X ^^ ammal burrow of the Siluro-Cam- 



, , ,, , brian, probably of a crustacean, a, Track 



made by the bur- connected with it. 

 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 Planulitcs are tracks and burrows of 

 worms, wif . or without marks of setae, and some of the 



* The name Bilobiies was originally proposed by Do Kay for a bivalve 

 shell {Conocardium). Its application to supposed Algfc was an error, 

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

 animal trails. 



