L. D. Burling — Protichiiites and Climactichnites. 395 



Y-shaped outward, abruptly truncated at right angles to the 

 longer diameter, and even arched inward ; {k) the " oval bodies " 

 are themselves frequently curved, even broadly S-shaped ; {I) 

 the apex of the Y-shaped transverse ridges always points toward 

 the '-oval bodies"; {m) the Y-shaped transverse ridges may 

 often be seen to extend nearly half way beneath the oval-body ; 

 {n) the trails are nearly always faint and disappear at the end 

 opposite to the one bearing the " oval body." 



Inferences : {a) the side ridges were apparently made in the 

 same push that made the transverse ridges, and that both are 

 ridges instead of furrows indicates that the apex of the 

 Y-shaped ridges points backward with reference to the line of 

 progress, for this is the only direction in which material could 

 be shoved outward and heaped up along the edges of the trail ; 

 (h) in all probability these figures represent the entire width of 

 the animal ; (c, d^ and e) the portion of the animal making the 

 transverse ridges was very flexible and capable of making move- 

 ments differing in amplitude, direction, and form ; the inter- 

 ruptions in the center (d) are to be expected, and do not 

 require a division of the ridge-forming portion, a view which 

 is corroborated by the wide lateral shifting exhibited by this 

 median ridge ; {f) these semicircular raised lines must have 

 been made last or they would have been obliterated or marred, 

 and must indicate the conformation of the back end of the ani- 

 mal ; their close spacing would indicate slowness of forward 

 movement or creep ; {g) the apex of the Y-shaped ridges there- 

 fore points also toward the rear; (A) probably made, as Todd 

 suggests, by bristles or other portions of the under surface as 

 the animal moved along, — I have not observed them ; [i) the 

 animal, or its ambulatory organ, was very flexible, or else short 

 and more or less elliptical in outline ; [j) the evidence seems 

 to warrant us in disagreeing with the concensus of previous 

 opinion (seep. 391), and in supposing these oval bodies to repre- 

 sent the initial resting place of the animal that made the trails, 

 the round ends, as indicated in a andj'^, being the rear and the 

 Y-shaped end the front. This front end was capable of being 

 moved from Y-shape forward (its position in repose) to 

 Y-shape backward, and this movement carried the animal 

 along. The convexity of these oval bodies may be explained 

 as follow^s : If an animal with a very flexible under surface or 

 foot were stranded on the retreat of the tide, scour would 

 obliterate the previous tracks and would reduce the general 

 level of the beach wherever it w^as not protected from erosion 

 by the disk-like foot, and the edges of this organ would natu- 

 rall}^ be depressed in an endeavor to prevent being washed 

 away. The lens of sand thus enclosed would be left upon the 

 departure of the animal at the approach of the next tide, its 



