L. D. BiiHmg — Frotichnites and Climactichnites, 387 



Art. XXXIY. — Frotichnites and Climactichnites ; A Criti- 

 cal Sttcdy of Some Cambrian Trails '^"^ by Lancaster D. 

 Burling. 



JuDaiNG the nature of the maker of a trail by peculiarities 

 in its composition may be difficult and the solution false — for 

 example, the writer has watched the larvae of the common 

 may-fly crawling along the mud on the tidal flats of the St. 

 Lawrence and leaving a perfectly smooth sinuous trail or 

 groove which would naturally be associated in the mind of 

 almost anyone with the work of a worm, certainly nothing 

 with the legs of a may-fly larva. That the Upper Cambrian 

 sea was peopled by animals of large size is well known, but the 

 trails upon which this inference is based have so far failed to 

 indicate the true nature of their makers. Indeed they have 

 been the subject of frequent and widely variant conjecture. A 

 critical study of some of the trails in the Cambrian has yielded 

 conclusions so substantial or so different from those in the 

 literature that they appear to be worthy of record. 



Protichnites. 



The trails to which this name has been applied were referred 

 to the agency of a tortoise by Owen\f who later* assigned them 

 to the work of a crustacean like Limulus. In this view he 

 was followed by Dawson^ and Dana." Dawson later^ assigns 

 them indubitably to the work of crustaceans, but lessens the 

 weight of this reference by suggesting that Climactichnites 

 may have been made by the same animal. With the exception 

 of Chapman,^ who suggests that both Frotichnites and Climac- 

 tichnites are of fucoidal origin, succeeding authors, beginning 

 with Billings in 1870,^ have referred them to the work of trilo- 

 bites. Packard^ thinks they could " perhaps have been made 

 by the extremities of the feet of a small shrimp-like creature." 

 Later^ he questions the ability of Paradoxides to make the 

 trail, a question flrst raised by Dawson.'" Walcott^' unhesitat- 

 ingly states that they " were made by trilobites of the genus 

 DicellocephalusP 



Let us look at the trails themselves and see whether or not 

 their critical study may not yield results of tangible value in 

 the identiflcation of their makers. Frotichnites (see fig. 1) 

 is characterized by two rows of footprints paralleling a 

 median groove. They have been found on Upper Cambrian 

 sandstones in Ontario and New York. The trails give us 

 several clues as to the animal which made them, and these facts 



* Published by permission of the Deputy Minister of Mines, 

 f For references, see the literature at end of article. 



Am. Jour. Sci.— Fourth Series, Vol. XLIV, No. 263. — November, 1917. 



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