1852.1 LOGAN POTSDAM SANDSTONE FOOT-PRINTS. 201 



sandstone throughout the Canadian portions of its distribution already- 

 mentioned ; and it is stated by Mr. Hall that the same characteristic 

 accompanies the Potsdam sandstone in New York and Pennsylvania, 

 and as far as Tennessee. 



With this part of the formation also are associated many indications 

 of what have been considered as Fucoids. One form among others 

 presents a reticulated arrangement of stem-like bodies spreading 

 over some of the surfaces, the interspaces of the network being four-, 

 five-, and six-sided, and sometimes, when largest, measuring 1 4 inches 

 in diameter ; while the ridges which divide them are an inch and a 

 half wide, and stand out half an inch in relief on the sandstone. 

 The compartments are sometimes filled with shale, and the low 

 ridges, a good deal resembling crack-casts, might be taken for such, 

 were not similar forms occasionally traceable on splitting open 

 closely joined surfaces of sandstone where no shale intervenes, and 

 were not smooth surfaces of arenaceo-bituminous limestone in the 

 succeeding formation met with presenting black bituminous pellicles 

 arranged in similar reticulated figures — both large and small. 



At Beauharnois, in the locality in which the first Track was dis- 

 covered, and on a bed in the same quarry, the trail of a Worm or of a 

 Mollusk was very beautifully displayed ; and in the Johnstown District 

 not only do Scolithus and Fucoids exist in abundance, but my asso- 

 ciate, Mr. Murray, has there met with Lingula antiqua, characterizing 

 this part of the formation, as it does also at Hammond on the south 

 side of the river. 



The new localities in which foot-prints have been met with are five 

 in number. In none of them is Lingula found immediately near, but 

 Scolithus abounds in them all, as well as the Fucoids. Two of the 

 new localities are in the vicinity of Beauharnois (see Map, PL VI.) ; 

 one of these, in the field of Mr. Henault, is about half-a-mile west- 

 ward of that in which the first impressions were discovered ; the 

 other about two-and-a-half miles still further westward, and about 

 500 yards from the mouth of the Beauharnois Canal. Scolithus and 

 Fucoids are seen in beds a few feet above and a few feet below those 

 having the foot-prints, and 7 feet below one of them the Worm-holes 

 are accompanied by a thin band of interstratified limestone. Along 

 the shore of Lake St. Louis, between the two localities, the sandstone, 

 with the occasional appearance of a calcareous layer, can be seen 

 nearly the whole distance, and a careful admeasurement of the distance 

 and of the minute changes that occur in the very moderate dips 

 prevailing enables me to bring the track-bearing beds to within 3 feet 

 of one another in stratigraphical place, while geographically their 

 positions are equivalent in relation to the Calciferous Sand-rock whicli 

 on each side bounds the more siliceous formation. 



Proceeding eastward from the exposures in Henault' s field and the 

 tracks on the St. Louis River (those first discovered), the sandstone, 

 marked by Scolithus, can be followed along-shore for about a mile, 

 and is very nearly flat. Then there is an interval of about a mile 

 without any exposure, beyond which the Calciferous Sand-rock first 

 makes its appearance. Thin interstratified bands, more arenaceous 



