NO. 9 NEW YORK POTSDAM-HOYT FAUNA 2/7 



that of Liitndus, proportionately stronger and perhaps more divided feet, and 

 a stouter caudal spine. 



Mr. E. Billings in 1870^ concluded that : 



1. The tracks could have been made either by a Liniulus or by a trilobite. 



2. No fossils of the order (Ziphosura) to which LimtUus belongs have been 

 found so low down as the Potsdam sandstone. 



3. Large trilobites occur there in abundance. 



The weight of evidence, therefore, favors the opinion that the tracks in 

 question are those of trilobites. 



Prof. E. J. Chapman in 1877 " broached the view that the tracks 

 named Protichnites and Climactichnites were of fucoidal origin. I 

 will refer to this view again under Climactichnites (see p. 278). 



In a very fine paper on burrows and tracks Sir J. William Dawson 

 in 1890' stated that the Protichnites of the Potsdam sandstone are 

 indubitable tracks of crustaceans, and that both Protichnites and 

 Climactichnites may have been made by the same animal. 



My own interest in the tracks began in 1886 when I first met with 

 them north of the Adirondack Mountains in Beauharnois, Canada, 

 and on the eastern side of the mountains in Essex County, New York. 

 At the Beauharnois locality, west of the town, on Rogier's farm I 

 obtained fine specimens of the Protichnites tracks, showing that 

 many of the impressions were trifid (pis. 46 and 47) and made by a 

 crustacean having legs terminating in a joint that had three strong, 

 narrow, tenninal spines. It was this trifid aspect of the tracks that 

 probably led the first observers to consider that the tracks might have 

 been made by a three-toed vertebrate similar to the tortoise. For 

 twenty-six years I have had the specimens, or photographs of them, 

 in my laboratory, waiting for something to turn up that would 

 explain more satisfactorily not only the complicated and varied 

 series of tracks described by Owen, but also the trifid impressions 

 illustrated on plates 46 and 47 of this paper. The explanation came 

 with the discovery in 191 1 of the series of appendages of the 

 trilobite Neolenus serratus (Rominger). On plate 45, figure i, is 

 shown a series of the legs on the left side of the trilobite extending 

 far beyond the margin of the dorsal shield. In figure 2, the ter- 

 minal joints of several of the legs have three terminable, movable, 

 slightly curved spines. The cephalic legs of figure 3 project for- 

 ward from the side of the cephalon, and figure 4 shows the trifid 

 arrangement of the short, strong spines of the terminal joint of the 

 cephalic legs. 



^ Quart. Journ. Geol. Soc. London, Vol. 26, 1870, pp. 484-485. 



^ Canadian Journ. Sci., Lit., and Hist., new ser., Vol. 15, 1877, p. 490. 



' Quart. Journ. Geol. Soc. London. Vol. 46, 1890, p. 599. 



