32 



Forty-second Annual Report on the 



not yet discovered any certain drifted vestige of its plants along 

 many hundred miles of its coast. 



" The crustacean which impressed the tracks at Beauharnois must 

 have been a littoral animal, tracks of which have now been found in 

 several places nearer than Beauharnois to the marginal limit of the sea 

 to which it belonged. These localities are St. Ann, Vaudreuil, Pres- 

 qu'ile, Lachute and St. Elizabeth, and they were last year observed in 

 the neighborhood of Perth. In the last locality they are associated 

 with a new and remarkable description of track for the discovery of 

 which we are indebted to my friend Dr. James Wilson of Perth, who 

 sent me specimens of it in the month of November last. 



" The largest of the specimens was between two and three feet long 

 by a foot wide, and the track upon it so singular that I became 

 desirous of obtaining a greater extent of the trail. For this purpose, 

 in the beginning of December, I sent Mr. Richardson to Perth, where 

 he was guided to the quarry by Dr. Wilson, and shown the bed in 

 which the tracks occur. The quarry, of which the strata are nearly 

 horizontal, is about a mile from the town, and with the aid of Mr- 

 Glyn, the proprietor, Mr. Richardson obtained in fragments, a surface 

 which measures about seventy-six square feet. To obtain this 

 required a good deal of patience, for there was half a foot of snow on 

 the ground, and from under this it was necessary to remove between 

 two and three feet of rock in order to reach the bed. The rock is a 

 fine-grained white Sandstone similar to that in which the Protichnites 

 occurs at Beauharnois, and of that pure silicious character which is so 

 well known to belong to the Potsdam formation wherever it is met 

 with. The tracks are impressed on a bed which varies in thickness 

 in different parts from one-eighth of an inch to three inches. When 

 the upper bed was removed, large portions of the track-bearing bed 

 came away with it, and it was necessary to separate the layers. This 

 was done by heating the surface with burning wood placed upon it, 

 and then suddenly cooling it by the application of snow. This, of 

 course, cracked and destroyed the thin bed with the impressed tracks, 

 but it left the mold of them on the under side of the upper bed, and 

 by plaster casts from this we have obtained the true form of the 

 original tracks. 



M These tracks consist of a number of parallel ridges and furrows 

 something like ripple marks, which are arranged between two narrow 

 continuous parallel ridges, giving to the whole impression a form very 

 much like that of a ladder, and as the whole form is usually gently 

 sinuous it looks like a ladder of rope. The surface obtained shows 

 six different trails (Fig. 1), the longest of which is about thirteen feet, 



