PALEONTOLOGICAL NOTES, NO. VI. 



ON SUPPOSED MEROSTOMATOUS AND OTHER PALEO- 

 ZOIC ARTHROPOD TRAILS, WITH NOTES ON THOSE 

 OF LIMULUS. 



By Alpheus S. Packard. 



Presented May 9, 1000. Received May 22, 1900. 



Trails or tracks evidently made by paleozoic arthropods have occurred 

 most abundantly in the Potsdam sandstone (Cambrian) of Canada and 

 New York, also in the Hudson River or Cincinnati stage of the Ordovi- 

 cian Period. We have now to add descriptions of tracks of a similar 

 nature from the Chemung stage (Upper Devonian) and from the Upper 

 Carboniferous. We will give the name trail to the entire series of foot- 

 prints, and restrict the word track to the individual footprints. The trails 

 discovered by Logan, and carefully described by Professor R. Owen,* 

 were very large, being six inches wide and several feet long, and were 

 evidently made by some large trilobite (as first suggested by Dana) 

 witb a caudal spine, as there is a well-marked median furrow. Whether 

 the trilobite was a Paradoxides or not is uncertain, because the species 

 of this genus are without a definite caudal spine, such as is to be seen in 

 Dalmanites and certain other trilobites of a later period than the Cam- 

 brian. But aside from this the tracks, in sets of seven and eight, seem 

 most probably to have been made by an arthropod with numerous pairs of 

 jointed cylindrical legs, such as we now know, through the researches of 

 Walcott and of Beecher, trilobites possessed. Professor Owen described 

 six species of the tracks, for which he proposed the generic name of 

 Protichnites, but we venture to suggest that it is not improbable that 

 they were all made by a single species of trilobite, as observation has 

 taught us that Limulus may make tracks of very dissimilar shape. We 

 would suggest that to trails consisting of sets of several, or as many as 



* Journal Geolog. Soc. London, VIII. pp. 199, 214. 1852. 



These trails, Protichnites septem-notatus Owen, are figured on a reduced scale in 

 Dana's Manual of Geology, Fig. 25G ; and P. octonotatus Owen in the new edition 

 of Bronn's Lethaja geognostica. 



