280 Wisconsin Academy of Sciences, Arts, and Letters. 



It is possible, however, that the difference is owing mainly, if 

 not entirely, to a difference of the medium in which they were 

 found. These Wisconsin tracks, as before implied, were formed 

 in loose sand, composed of rounded grains. Similar animals, 

 moving upon mud, would probably push up, on either side of 

 the track, a ridge of sufficient consistency to stand. We are not. 

 informed as to the character of the rock in which the Canada 

 tracks are found. 



For convenience for future reference, the larger tracks described,- 

 showing occasional longitudinal and wavy markings, we would 

 provisionally name Climaciichnites Youngi; and under this would 

 include all the smaller ones, showing regular convex and V-shaped 

 transverse ridges. They may prove to have been formed by im- 

 mature individuals. The solitary track, pi. 1, below, with flat 

 and usually straight ridges, may be a variety of the same ; but 

 these differences, with others not easily expressed, seem sufficient 

 reason for designating it by another name, viz. — Climactichnites 

 Fosteri It should be distinctly understood that the names may 

 be discontinued, whenever the name of the species of animals 

 which formed them can be definitely and satisfactorily substi- 

 tuted. 



This paper would doubtless be considered incomplete, did it not 

 give at least some conjecture concerning the character of the ani- 

 mals which formed these tracks. (We say animals, for the sug- 

 gestion of Prof. Chapman, of Toronto, that Climaciichnites are- 

 impressions of Fucoids {vid. American Journal of Science, vol. 

 14, p, 240), clearly cannot apply to these under consideration. 

 The longitudinal lines and variations of th6 transverse ridges, ap- 

 pearing with such irregularity, forbid the idea.) 



Endeavoring to confine ourselves strictly to the facts, and the- 

 most patent inferences therefrom, we conclude that, whatever the 

 nature of the animals and whatever the form of their anterior 

 ambulatory organs, those leaving the last impressions were very 

 perfectly flexible. This is shown in the very variable form of the 

 transverse ridges, as noted above. 



They must have been in pairs, and each capable of motion, in- 

 dependent of its fellow. This is proved by the intercalated ridges. 



