422 ROYAL SOCIETY OF CANADA 



ACEIPES n. gen. 



This type of footprint is quite different from those above described, 

 -and similar to those which have been called " crustacean." To the author, 

 however, these prints appear to be impressions made by insects or arach- 

 nids, more probably the former, and if these insects were stout-bodied 

 and apterous there would be the greater reason to suppose they might 

 make tracks such as these are. 



It is diflScult to find indications as to which is the forward end of 

 these tracks. A steeper slope is oftener found on one side of the indi- 

 vidual footprints than on the other and this steeper slope we take to be 

 the posterior slope of the footprint. Furthermore on this side the sur- 

 face of the shale is sometimes raised outside the footprint, as though 

 pressed upward by the impact of the foot in the impression in front. 



Taking these indications as showing which is the front and which 

 the back of the animal's track it may be described as follows : — 



Imprints of footmarks of the feet of two sides of the body; these 

 prints follow each other closely, those of the right side mostly puncti- 

 form and circular, or triangular; those of the left side more elongate 

 transversely, the animal had a habit of changing the position of the feet 

 on this side so that the imprints are doubled for about three imprints; 

 this duplication is sometimes found also in the footmarks of the right 

 side. 



AcEiPEs iNCERTiPES n. sp. Plate Til, Figs. 1 and 2. 



This track is remarkable for the diversity in form of the footmarks 

 on the two sides of the body. 



On the right side the row of tracks runs with reasonable regularity 

 from one end of the series to the other; but on the left side the tracks 

 are broken in sets of about nine footmarks, set " en echelon." Where 

 the break occurs there are three footmarks that are doubled, three in each 

 series being parallel, as though these three feet had been lifted and set 

 down a second time outside of their first position. 



The footmarks of the two sides of the track have a different form; 

 those of the right side were triangular with the inside angle most deeply 

 impressed. This right side footprint seems to be composed of the im- 

 pression of two points or claws, one turned inward at right angles to the 

 general course of the track; the other pointing backward and outward. 



The footprints on the left side show only the transverse imprint 

 which is much longer than the corresponding impression of the right side 

 footprint, and is bent forward at the inner end, giving the footprints on 

 this side a bowed form. 



On the left side where the footprints are doubled, the first one of the 

 new series is more weakly impressed than the others. 



