396 L. Jj. Burling — Protichnites and Climactichnites. 



preservation, and that of the tracks made in moving away, 

 being due to fortnitons circumstances; (Jc) corroborates i in 

 proving the animal or its foot to be extremely flexible ; (l) 

 therefore, if we are right in a^ f^ and J, the apex of the Y 

 always points in the direction from which the animal has been 

 moving, not forward as nearly everyone has supposed, Patten*^ 

 being the only one to suggest a possible difference ; (m) unless 

 the ambulatory organ or organs occupied nearly half of the 

 under surface this fact alone would prove that the animal 

 moved away from the oval-body end. The preservation of 

 these marks in the portion of the trail where the body mnst 

 have rested seems to the writer to be explained by supjDosing 

 the edges of the disk-like foot to be sufliciently extended in 

 repose to protect the last marks made by the animal previous 

 to its rest — the oval body is frequently about one fifth wider 

 than the immediately adjacent trail ; {71) the progressive faintness 

 and disappearance of the trails at the end opposite to that 

 bearing the oval bodies is characteristic of nearly all of the 

 trails ; all of those, for example, which exhibit both ends in 

 the specimen at Albany/^ They certainly seem to corroborate 

 co^f\j^ and m^ in indicating that the animal started from the 

 oval-body end and rose into the water at the other end, as 

 pointed out by Patten," and that they could swim. 



In some trails, notably the one running down the center of 

 the slab in the museum at Albany, the disposition of the ridges 

 is such as to suggest that the animal did move toward the oval 

 body end of the trail. The impressions of the curved margin 

 described under y on a previous page were unknown to geolo- 

 gists until the specimen from New Lisbon, Wisconsin, was 

 figured by Walcott in 1912, and while Walcott adheres to the 

 belief that the Xew Lisbon animal also moved toward the oval- 

 body end we have endeavored to show that this specimen 

 proves the oval body end to be the initial portion of the trail. 

 The V-shaped ridges in l)otli the Albany and ]^ew London 

 specimens point toward the oval-body end, and it is somewhat 

 improbable that the animal should have inoved toicard that 

 end in the one case and awaij from it in the other. However, 

 there are certain differences in the trails, and these may be due 

 either to causes dependent on the physical conditions at the 

 time the trails were made or to differences in the animals 

 themselves. The^'^ew Lisbon specimen certainh^ started from 

 the oval body end to crawl away; those in the Albany slab 

 mav have come to rest in the manner described by the early 

 observers. Naturally, however, the conclusion that the oval- 

 body end was made last has called forth attempts to explain 

 the disappearance of the animal. 



