GEOLOGY. 281 



FOOTPRINTS IN THE OLD RED SANDSTONE. 



MR. ISAAC LEA, of Philadelphia, gives the following account of the 

 discovery of fossil footprints in the old red sandstone near Pottsville, 

 Pa. In examining the strata in the gorge of the Sharp Mountain, 

 where the Schuylkill breaks through it, he was astonished to find, on 

 a large mass of old red sandstone, six distinct impressions of foot- 

 marks in a double row of tracks, each mark being duplicated by the 

 hind foot falling into the impression of the fore foot, but a little in ad- 

 vance of it. The strata were tilted a little over the vertical, and the 

 surface of the rock exposed was about twelve feet by six, the whole 

 of which was covered with ripple-marks and the pit of rain-drops, 

 beautifully displayed in the fine texture of the stone. The six double 

 impressions distinctly showed, in the two parallel rows formed by the 

 left feet on the one side, and the right on the other, that the animal 

 had five toes on the fore feet, three of which toes were apparently 

 armed with unguical appendages. The length of the double impres- 

 sion was 4^ inches, the breadth 4 inches, the distance apart in the 

 length of the animal's step 13 inches, and across from outside to out- 

 side 8 inches. The marks of the dragging of the tail were distinct, 

 but occasionally slightly obliterated a small part of the impressions of 

 the footmarks. The footmarks assimilate remarkably to those of the 

 recent alligator of the Mississippi. No such animal remains have 

 heretofore been found so low in the geological series, so that these 

 footmarks are of great interest. Their position was about 8,500 feet 

 below the upper part of the coal formation at Pottsville, and by vari- 

 ous measurements about 700 feet below the surface of the old red 

 sandstone. Mr. Lea has named the animal supposed to have made 

 these footmarks Sauropus primcevus. The limestone of the old red 

 sandstone exists at the locality where the footmarks were found; it 

 is about 2 feet thick, and underlies the footmarks about 65 feet. 



DRIFT FOSSILS FROM NANTUCKET. 



A LOCALITY of drift fossils has been discovered by Mr. Desor, in a 

 cliff at the east end of Nantucket island. The outlines of the strata 

 of the cliff are somewhat obscured by the sand which has been blown 

 over the surface, but about half way up is an oyster-bed, containing 

 many fossils in a remarkably perfect condition ; even crab's claws be- 

 ing found here unbroken. Its position indicates that it has not been 

 disturbed since it was formed. It contains most of the species found on 

 the neighbouring beaches. Specimens of Venus are sometimes found 

 with the valves open, as if from the relaxation of the muscles at the 

 moment of death. 



Until within a few years, it has been supposed that there were no 

 fossils in the drift south of Lake Cham plain. In 1847, Mr. Desor 

 discovered a fossil deposit on Long Island, the origin of which was 

 doubtful, as the shells were much broken and worn. But at Nan- 

 tucket, a point between these localities, the formation is now found to 

 exist without the least trace of disturbance. The strata at the east 



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