652 BEPORT— 1886. 



the attempt was made in Europe more critically to define and classify these objects, 

 a great divergence of opinion developed itself, of which the recent memoirs of 

 Nathorst, Williamson, Saporta, and Delgado may be taken as examples. 



The author, acting on a suggestion of Sir 11. Owen, was enabled in 1862 and 

 1864, by the study of the footprints of the recent Limulus jiolyphemus, to show 

 that not merely the impressions known as Protichnites and Climactichnites, but also 

 the supposed fucoids of the genera Rusophycus, Arthrophycus, and Cruziana are 

 really tracks of Crustacea, and not improbably of Trilobites and Limuloids.' He 

 had subsequently applied similar explanations to a variety of other impressions 

 found on Palaeozoic rocks.' The object of the present paper was to illustrate by 

 a number of additional examples the same conclusions, and especially to support 

 the recent results of Nathorst and Williamson. 



Rusichniles, Arthi-ichniies, Chrossochorda, and Cruziana, with other forms of 

 so-called JBilobites, are closely allied to each other, and are explicable by reference 

 to the impressions left by the swimming and walking feet of Limulus, and by the 

 burrows of that animal. They pass into Protichnites by such forms as the P. 

 Davisii of Williamson, and Saerichnites of Billings, and Diplichnites of the author. 

 They are connected with the worm-tracks of the genus Nereites by specimens of 

 Arthrichnites, in which the central furrow becomes obsolete, and by the genus 

 Gyrichnites of "^^^liteaves.* 



The tuberculated impressions known as Phymatoderma and Caulet-pites may, as 

 Zeiller has shown, be made by the burrowing of the mole-cricket, and fine examples 

 occurring in the Clinton formation of Canada are probably the work of Crustacea. 

 It is probable, however, that some of the later forms referred to these genera are 

 really algae related to Cauleiya, or even branches of Conifers of the genus Brachy- 

 phyllum. 



Nereites and Planvlites are tracks and burrows of worms, with or without 

 marks of setae, and some of the markings referred to P(dccochorda, Palceophycus, 

 and Scolithus have their places here. Many examples highly illustrative of the 

 manner of formation of these impressions are afforded by tJanadian rocks. 



Branching forms referred to Licrophycus of Billings, and some of those referred 

 to Buthotrephis, Hall, as well as radiating markings referable to Scotolithus, 

 Gyrophyllites and Asterophycus, are explained by the branching burrows of worms 

 illustrated by Nathorst and the author. Astropolithon,oi \h& Canadian Cambrian, 

 seems to be something organic, but of what nature is uncertain. 



Rhabdichnites and JEophyton belong to impressions explicable by the trails of 

 drifting seaweeds, the tail-markings of Crustacea, and the ruts ploughed by bivalve 

 mollusks. 



Dendrophycus, Dictyolites, some species of Delesserites, Arisfophycus, and other 

 branching and frond-like forms, were shown to be referable to riil-marks, of which 

 many fine forms occur in the Carboniferous of Nova Scotia, and also on the recent 

 mud-fiata of the Bay of Fundj'. 



The genus Spirophyton, properly so called, is certainly of vegetable origin, but 

 many markings of water action, fin-marks, &c. have been confounded with these 

 so-called ' Cauda-galli fucoids.' 



On the other hand some species of Palceophycus, ButJioirephis and Spheno- 

 thallus were shown to be true algaj, by their forms and the evidence of organic 

 matter, and Haliserites, Barrandeina, and Nematojihycus were shown to include 

 plants of much higher organisation than the algae. With reference to the latter, 

 it was held that the form to which the name Prototaxites had been given was really 

 a land plant growing on the borders of the sea, and producing seeds fitted for 

 flotation. On the other hand, certain forms to which he had given the name 

 Nematoxylon were allied to algae in their structure, and may have been of aquatic 

 habit ; verj- perfectly preserved specimens of these last had been recently found, and 

 had thrown new light on their structure. 



' ' On Footprints of Limulus,' Canad. Nat. 1863. ' On the Fossils of the Genus 

 Rusophycus,' ibid. 1864. 



2 ' On Footprints and Impressions of Aquatic Animals,' Am. Journ. of Science, 

 ' Trans. Royal Society of Canada, 1883. 



