1852.] LOGAN POTSDAM SANDSTONE FOOT-PRINTS. 207 



surface, another escarpment rises to the height of 70 feet. The white 

 sandstone, perforated with Scolithus, is seen at the base, interstratified 

 with calcareo-arenaceous beds for about 25 feet up, and these calcareo- 

 arenaceous beds, holding geodes of calc-spar, compose the remainder 

 of the rise. About 300 yards further, after a very gentle slope, 

 there is a smaller step, composed of the same description of calca- 

 reous sandstones, and from this a level surface, of about a quarter 

 of a mile broad, in which similar strata are seen once, reaches a small 

 rise of 5 feet, composed of an arenaceous limestone, which is quarried 

 for burning. In the quarry occurs Ophileta levata of Vanuxem (a 

 Calciferous Sand-rock species) and Raphistoma (the same as that of 

 St. Ann's section) ; and the general dip in the section is such as to 

 leave no room to doubt the place of the track-bed, which would be 

 about 160 feet beneath the limestone. 



Farther south this line is covered up by sandy drift for several 

 miles, but, if we go about five or six miles to the westward, and again 

 starting from the gneiss, take a course at right angles to the strike 

 (Section 4 of the Map), three and a half miles will bring us to a two- 

 feet bed of good limestone. This rock, from its having been quarried 

 for lime-burning in several places, has been followed from Carrillon 

 to Grenville (thirteen miles) . The dip of the limestone from its out- 

 crop to the river (two miles) is about 7^ feet in a mile. That it 

 overlies the beds of the previous section is not considered uncertain ; 

 from the paucity of exposures, however, between it and the gneiss, 

 and the increased dip near the gneiss, it is not easy to determine its 

 relative position. It may be at least 150 feet higher ; for there are 

 seen in some of the naturally exposed sections of the Ottawa very 

 nearly 100 feet of underlying calcareous claystone, weathering more 

 or less yellow or brown, and in some parts bituminous and in others 

 arenaceous, and often presenting in the latter case geodes of calc-spar 

 and heavy-spar ; and none of these beds appear in the Riviere du 

 Nord section. Immediately beneath the 2-feet limestone there is a 

 singular and extensively spread concretionary layer, in some large 

 exposures of which, surfaces of half an acre show these concretions, 

 consisting of concentric layers, cut in half and closely packed to- 

 gether, some of them being 2 to 3 feet in diameter. The limestone 

 bed is fossiliferous, and displays Maclurea sordida (a Calciferous 

 Sand-rock species), Pleurotomaria nodulosa ? (a Bird's-eye species), 

 Murchisonia bicincta, and another species, an Atrypa allied to A. ex- 

 tans, Raphistoma, Turbo, Modiola, Orthoceras, Leperditia Cana- 

 densis (Jones, MS.), and Beyrichia Logani* (Jones, MS.), in abun- 

 dance, and a new species of Paradoxidesf ; and at a short distance 

 above the bed there are about 50 feet of sandstone, with bands of 

 green shale, holding a vast collection of Fucoids, of which a bilo- 

 bated species is most conspicuous. Some of the sandstone beds are 



* Occurring also at Hawkesbury. 



t The head is not perfect, but, from the general character of the glabella and 

 eyes, Mr. Salter has little doubt that it belongs to Paradoxides. That genus, 

 however, has not yet been noticed in America. 



p2 



