66 THE CANADIAN NATURALIST. [Vol. vil. 



the American Limulus (PoJi/j^hemus occidentalis). I proved by 

 experiment with the modern animal that the recurring series of 

 groups of markings were produced by the toes of the large 

 posterior thoracic feet, the irregular scratches seen in Protichnites 

 lineatus by the ordinary feet, and the central furrow by the 

 tail. It was also shown that when the Limulus uses its swim- 

 ming feet it produces impressions of the character of those named 

 ClimacticJmifes, from the same beds which afford Protichnites. 

 The principal difference between Protichnites and their modern 

 representatives is that the latter have two lateral furrows pro- 

 duced by the sides of the carapace, which are wanting in the 

 former. • 



As Limuloid crustaceans are well known in the Carboniferous 

 beds of Europe and America, their footprints might be expected 

 to occur in rocks of this age, but the first I have met with were 

 sent to me last summer by my friend Mr. Elder, of Harvard 

 College, who found them quite abundantly in dark-colored flag- 

 stones belonging to the Millstone Grit formation at McKay's 

 Head in Nova Scotia (fig. 1). The animal which produced 

 these marks must have been of small size (about half an inch in 

 breadth), in this agreeing with the usual size of the Coal-for- 

 mation Limuloids; and like the ancient Pro tichnite makers, it 

 left no trace of the edges of the carapace, but a very distinct 

 impression of a sharp pointed tail. Its posterior feet had three 

 or possibly four sharp toes. There were besides several pairs of 

 sharp-pointed walking feet. On the same slabs there are some 

 series of marks, evidently made by the same kind of animal, 

 which have no tail-mark, and there are tail-marks with only 

 traces of those of the toes. It is worthy of notice that, though 

 these tracks indicate the presence of the animal, no crusts of 

 Carboniferous Limuloid crustaceans have yet been found in Nova 

 Scotia. The sand in which the tracks now referred to were 

 made was probably too hard to permit the swimming feet to 

 make any impression. AVith respect to the absence of the 

 marks of the sides of the carapace, I may observe that the 

 genus Belinurus of the Carboniferous had the sides of the cara- 

 pace less deep than that of the modern Limulus, and this may 

 also have been the case with the more ancient Limuloids of the 

 Potsdam. See as to this a letter by Prof Hall in the Canadian 

 J^aturaUst, 1862. 



To Protichnites may perhaps be referred a very singular 



