36 Fossils of the Potsdam Sandstone. 



inches apart and each corresponds to the impressions made by the feet upon 

 one side of the animal. The wood cut (Fig. 3) is copied from one of the 



large engravings in the jour- 

 nal of the Geological So- 

 ciety for 1853. It repre- 

 sents, on a small scale, the 

 tracks of the species which 

 Professor Owen has called 

 Protichnites septemnota^ 

 tus, or the " seven marked"' 

 Protichnites. In the ori- 

 ginal, the width of the 

 track measured across from 

 the outside of the rows of 

 foot-prints, is five inches. 

 The length of the portion 

 figured in the journal is 21^ 

 inches. « 



This species appears to 

 have been a small animal, 

 fiat like a tortoise, but with 

 seven legs upon each side. 

 In walking, the foot-prints 

 made by the feet upon one 

 side of a quadruped, are 

 never opposite those made 

 by the feet of the other 

 side. But in the tracks of 

 Protichnites they appear to 

 be exactly opposite. It is 

 difficult to understand how 

 this could be effected, un- 

 less we suppose the animal 

 to rest itself between every 

 step upon the ground, and 

 raise all its legs, move them 

 forward and put them all 

 down at once, in the way 

 that several men in a boat 

 raise all the oars at the 

 same time. It seems thus 

 to have rowed itself, as it 

 II were, along the sand. If 

 U such were its mode of pro- 



; jrression,, then between every step we should expect to find the groove made 

 ' by dragging it^ body along deep, where the whole weight rested upon the 



