276 Wisconsin Academy of Sciences, Arts and Letters. 



A DESCEIPTION OF SOME FOSSIL TRACKS FBOM 

 THE POTSDAM SANDSTONE. 



Bt Prof. James E. Todd.i 



1 At the winter meeting of tlie Academy in 1879, a verbal description and 

 discussion of these tracks, illustrated by photographs, was presented by Prof. 

 T. C. Chamberlin, but the pressure of other work preventing the preparation 

 of a description for the press, the matter was placed in the hands of the 

 writer. The names here adopted are those then, proposed. The specimens 

 on which the descriptions are based — in all about half a ton of slabs — are 

 in the cabinet of Beloit College, and were procured through the kindness of 

 Mr. Young and at the expense of Mr. Chamberlin. 



Several months since, Rev. A. A. Young of New Lisbon, Wis., 

 called the attention of the state geologist to some very interesting 

 fossil tracks, that occur at two quarries located near the Lemon- 

 weir river. They are about four miles north of the village of 

 New Lisbon. The geological horizon is the upper portion of the 

 Potsdam, The rock upon which they are impressed is a medium- 

 grained, compact, hard, silicious sandstone, which splits readily 

 into flags, three or four inches in thickness. The conditions of 

 its deposition are indicated by distinct, and often oblique lamina- 

 tion, and by ripple marks. No animal remains have yet been 

 found associated with the tracks, though these are remarkably 

 well preserved. 



1. The general appearance of the tracks is of , broad serpentine 

 bands crossing the stone, and sometimes so thickly as to obscure 

 one another, and give the appearance of an irregularly rippled 

 surface. 



The margins of the tracks appear to have been originally un- 

 broken lines, and parallel. ' The whole surface between these 

 lines has evidently been in contact with the animal making the 

 track, and there are no signs that any part of the animal reached 

 beyond these lines. 



2. The most conspicuous element of the track consists of a 

 clcsely consecutive series of nearly parallel, transverse ridges, 



