1852.] LOGAN POTSDAM SANDSTONE FOOT-PRINTS. 211 



convenient to illustrate the nature of the animal or animals by which 

 the foot-prints were impressed, I have brought over and temporarily 

 placed in the Museum of the Society the original slab of sandstone, 

 12y feet in length, from which the casts of last year's communication 

 were taken (No. 7 of Prof. Owen's description) ; a second slab of the 

 original stone, from Mr. Henault's' field, measuring 8 feet (No. 3 of 

 Prof. Owen's description) ; and a third slab, with two tracks and 

 ripple-mark upon it, from the Island of St. Genevieve. These are 

 accompanied by about 100 slabs of plaster-casts, taken from various 

 tracks as they are naturally exposed in the field. Adding one track 

 to another they measure about 350 feet. Two of the casts are from 

 tracks immediately near the one first discovered, and one of them 

 shows the groove running out of the centre (No. 4 of Prof. Owen's 

 description). The remainder are from Henault's field. In it four 

 areas are comprehended within a distance of four chains, three of 

 which are exhibited in their true relation to one another in PI. VII. 

 A, B, C ; and each of these is displayed on a larger scale, 3 inches 

 to 16feet, inPl. VIII. A, B, C. 



In PI. VIII. A. there are ten tracks, seven of them on a smooth- 

 surfaced bed, which has been rubbed by ice moving in a direction 

 S. 40° W. These tracks are indicated by lines of different colour, 

 and are numbered 1 to 7. Their measurements are, — 



(No. 5 of Prof. Owen's description.) 





ft. in. 





in. 



1. 



6 long by 5 wide. 



2. 



10 3 





5i „ 



3. 



28 6 





5i „ 



4. 



24 6 





4i .. 



5. 



8 6 





5i „ 



6. 



6 3 





5 „ 



7. 



12 





5 „ 



(No. 1 of Prof. Owen's description.) 

 (No. 6 of Prof. Owen's description.) 



96 



On a surface 2 inches lower, showing ripple-marks (the ridges of 

 the ripple-mark running N. 7b° E.), there are two tracks, numbered 

 9 and 10, measuring, 



ft. in. 

 9. 5 4 long, 

 10. 4 6 „ 



9 10 



And there is another, on a surface still lower by about 1 inch, but 

 showing no ripple-mark, 



ft. in. in. 



8. 4 6 long by 5^ wide. 



PI. VIII. B. shows seventeen tracks, twelve of which are on a 

 smooth surface, which has been rubbed by ice moving in a S.W. di- 

 rection. They are numbered 1 to 12, and measure 



