L. D. Biirling — Protichnites and Climactichnites. 391 



markings under consideration do not appear to have been made 

 by an animal provided with free movable limbs, or otherwise 

 with very short limbs, without the acute appendages belonging 

 to LhniiiusP Patten^^ was the iirst to suggest an Eurypterid 

 origin, " the abdominal gill plates making the rhythmic ridges 

 in the sand." Grabau and Shimer""^ assign the trails to the 

 work of "some unknown terrestrial or semi-terrestrial animal." 

 Authors are generally agreed that the oval bodies represent 

 the end of the trail ; thus Woodworth^° has suggested that they 



Fig. 2. 



Upper Cambrian Trail. 

 Fig. 2. CUmactichnites youngi (Chamberlin), 5/6 nat. size. (After Wal- 

 cott.) New Lisbon, Wis. U. S. Nat. Mus. 



(The front end of the trail is toward the bottom of the page.) 



represent the end of the trail, and Eastman^' states that " the 

 animal, if an Eurypterid, moved toward the sedentary impres- 

 sion and not away from it." Todd,'"" who apparently did not 

 have the opportunity of observing the oval bodies, records his 

 belief that the apex of the Y-shaped impressions points for- 

 ward, and Walcotf' speaks of the oval bodies as terminal and 

 (p. 284) of the forward-curving transverse furrows made by 

 pressing the beach-sand backward in creeping."'* The observa- 



