306 ANNUAL OF SCIENTIFIC DISCOVERY, 



been the modifications of the articulate type during a period probably 

 more remote from the secondary period than this is from the present 

 time '? In all probability there is no living form of animal, bearing 

 such a resemblance to that which the Potsdam sandstone foot-prints 

 indicate, as to enable us to illustrate its shape or its precise instruments 

 and mode of locomotion. 



The ripple-marks, which occur on surfaces so close in succession 

 among the track beds, run in a different direction on each surface, as 

 if they had been caused not by a current in deep water, running in 

 one general direction, but by a tide ebbing and flowing, and obeying 

 the influence of varying local accidental causes. On one surface was 

 observed the natural edge or termination of the ripple-ridges, with a 

 track coming up to it and there ceasing, as if the wave had reached 

 no farther, and one part of the surface had been dry while the water, 

 operating on another close by, had obliterated the track in producing 

 the ripple-mark. 



In connection with the discovery of these footprints, another singu- 

 lar discovery has been made, viz., the existence of phosphatic nodules 

 (containing between 36 and 67 per cent, of phosphate of lime, giving 

 off ammonia and an odor of burnt horn,) at the summit of the Hudson 

 River Group, at the base of the Chazy Limestone, and a little lower 

 in the calciferous sand-rock, where Lingulas and PleurotomariaB are 

 sometimes imbedded in the nodules. These nodules have also been 

 found in a conglomerate, which, from its position, is considered to be 

 older than the Cambrian, that constitutes the copper rocks of Lake 

 Huron, and also crystals of phosphate of lime, (apatite,) have been 

 noticed in a highly crystalline limestone interstratified with the gneiss, 

 which is the base rock of the country. 



Mr. Hunt, the chemist of the Survey, gives some additional facts 

 relative to those interesting discoveries. He states, that while recently 

 examining a coarse grained silicious sandstone and conglomerate, 

 which occurs near the river Ouelle, I detected several hollow cylin- 

 drical bodies which I supposed to be some hitherto unknown fossils, 

 and which you from their form, suggested to be possibly bones. A 

 chemical examination shows them to consist in great part of phosphate 

 of lime, and thus gives countenance to the idea that they are the 

 remains of vertebrate animals. The longest fragment found is about 

 an inch and a-half long, and one-fourth of an inch in diameter.' It is 

 hollow throughout, and filled with the earthy matter in which it is 

 obliquely imbedded, the disintegration of which by the weather, has 

 exposed the larger extremity of the foreign body, and a portion of its 

 interior. The smaller extremity is cylindrical and thin, but it grad- 

 ually enlarges from the thickening of the substance, and at the other 

 extremity becomes externally somewhat triangulariform ; the cavity 

 remains nearly cylindrical, but its sides are somewhat rough and 

 irregular. Two other fragments, presenting horizontal sections of 

 similar cylinders, were detected, having their other extremities in the 

 rock. The texture of these substances is compact, and the fracture 

 earthy. Their color is dark brown, but exhibits a yellowish-brown 



